Since 90: A settlement was established by Roman citizens at the Enz river near the modern Altstadter Brucke (old town bridge). Archeological surveys have unearthed several items from that period which are kept and displayed in the Kappelhof Museum. The settlement was located where the Roman military road connecting the military camp Argentoratum (nowadays Strasbourg in France) and the military camp at Cannstatt (now a suburb of Stuttgart) at the Upper Germanic Limes border line of the Roman Empire crossed the Enz river. This place was known as Portus (river crossing, harbor), which is believed to be the origin of the first part of the citys name "Pforzheim". A Roman milestone (the so-called Leugenstein) from the year 245 and later excavated at nowadays Friolzheim shows the exact distance to Portus; it is the first document about the settlement.
259/260: The Roman settlement Portus was destroyed completely, as the Frank and Alemanni tribes overrun the Upper Germanic Limes border line of the Roman Empire and conquered the Roman administrated area west of the Rhine river. From then on, over an extended period of time historical records about the settlement are not available.
6th/7th century: Graves from this period indicate that the settlement had been continued.
1067: The settlement of Pforzheim was mentioned for the first time in a document by Henry IV, Holy Roman Emperor as "Phorzheim". Visits to Pforzheim by Heinrich IV in 1067 and 1074 are documented.
Before 1080: The "old town" of Pforzheim was awarded market rights (Marktrecht). At that time Pforzheim belonged to the estate of Hirsau Monastery, according to monastery documents.
From 1150: Establishment of the "new town" west of the "old town" at the foot of the Schlossberg (palais hill) under Margrave Hermann V.
1200: The town charter of the "new town" was mentioned for the first time in a document. The "old town" continued to exist as a legally independent entity.
1220: The Margraves of Baden selected Pforzheim as their residence. The "new town" became prominent.
1240: A mayor of Pforzheim was mentioned in a document for the first time.
13th/14th century: Pforzheim enjoyed its first period of flourishment. A group of influential patricians emerged. They developed extensive activities on the financial markets of those days. The town drew its income from the wood trade, timber rafting, the tannery trade, textile manufacturing and other crafts. Documents mention mayor, judge, council and citizens. The town walls surrounding the new town were completed at about 1290. During this era three catholic orders established their convents in town (the Franciscan order established their domicile within the town wall at nowadays Barfuesserkirche (the choir of which remains), the Dominican nun order established their domicile outside of the walls of the old town near Auer bridge, and the Prediger cloister was located east of the Schlossberg, probably inside the town walls). Outside of the town wall across the Enz river, the suburb Flosser Quarters (the home of the timber floating trade) was established. Next to the western town wall, the suburb of Brotzingen gradually developed. The Margraves of Baden considered Pforzheim as their most important power base up to the first half of the 14th century. Under Margrave Bernard I (Bernhard I) Pforzheim became one of the administrative centers of the margraviate.
1322: Holy Ghost Hospital was founded at Trank Street (nowadays Deimling Street).
15th century: Various fraternities among people working in the same trade were established: The fraternity of tailors in 1410, the fraternity of bakers on May 14, 1422, the fraternity of the weavers in 1469, the fraternity of the wine-growers in 1491, the fraternity of the skippers and timber raftsmen in 1501, and the fraternity of the carters in 1512. Members of the same fraternity assisted each other in various ways, for example with funerals and in cases of sickness. In a sense, the fraternities were early forms of health and life insurance.
August 8–9, 1418: Sigismund, Holy Roman Emperor visits Margrave Bernard I (Bernhard I) in Pforzheim. On this occasion the mint of the Margraves of Baden in Pforzheim was mentioned. Mint master was Jakob Broeglin between 1414–1431. The emperor appointed the master of the Pforzheim mint, Jakob Broglin, and Bois von der Winterbach for five years as Royal Mint Masters of the mints of Frankfurt and Nordlingen. The Margrave was appointed as their patron.
1447: The wedding of Margrave Charles I (Karl I) of Baden with Katharina of Austria, the sister of Frederick III, Holy Roman Emperor (Friedrich III), was celebrated in Pforzheim with great pomp (including tournaments and dances).
1455: Johannes Reuchlin, the great German humanist, was born in Pforzheim on January 29 (he died in Stuttgart on June 30, 1522). He attended the Latin School section of the monastery school run by the Dominican order of Pforzheim in the late 1460s. Later, partly due to Reuchlins efforts, the Latin School of Pforzheim developed into one of the most prominent schools in southwestern Germany, named Reuchlin-Gymnasium. The schools teachers and pupils played an outstanding role in the dissemination of the ideas of humanism and the protestant reformation movement. The most famous pupils included Reuchlin himself, Reuchlins nephew Philipp Melanchthon, and Simon Grynaeus.
1460: Margrave Charles I established a kind of monastery (Kollegialstift) at the site of Schlosskirche St. Michael, turning the church into a collegiate church. There were also plans to establish a university in Pforzheim, but this plan had to be abandoned because Margrave Charles I lost the Battle of Seckenheim.
1463: Margrave Charles I was forced to transfer the palace and the town of Pforzheim as a fiefdom to the Elector Palatine after losing the Battle of Seckenheim. He then began to build a new palace in modern Baden-Baden. Margrave Christoph I finally moved the residence of the margraves to Baden-Baden. This gradually ended the first period of Pforzheims flourishment. The rich merchants gradually left the town, which declined to the status of a country town of mostly small traders. 
1486: The Weavers Ordinance (Wollweberordnung) for the towns Pforzheim und Ettlingen was approved by Margrave Christoph I. This was a contract concerning the town privileges of Pforzheim. This regulation of the weaving trade did not allow the formation of a regular guild (Zunft).
1491: A contract between Margrave Christoph I and the citizens of Pforzheim was concluded, granting the town of Pforzheim several privileges concerning taxes and business.
1496: Foundation of the first printers shop by Thomas Anshelm. During the first half of the 16th century Pforzheims printers contributed significantly to the establishment of this (in those days) new medium.
1501: Margrave Christoph I of Baden enacted the "Ordinance on the timber rafting profession in Pforzheim". The single timber logs that were floated from the deeper Black Forest areas down the Enz, Nagold and Wuerm rivers were bound together in the Au area to form larger timber rafts. Those rafts were then floated down the lower Enz, Neckar and Rhine rivers. The timber rafting stations of Weissenstein, Dillstein and Pforzheim were well known in the profession.
1501 was also the year for which an outbreak of the plague (probably the bubonic plague) is recorded in the Swabian chronicle Annalium Suevicorum by Eberhard Karls University of Tubingen professor Martin Grusius, published 1596. It is not known how many of Pforzheims citizens died in that year, but there are reports of 500 deceased in the close-by city of Calw and about 4000 in Stuttgart, which accounted for approximately one quarter to one half of the populations of those towns. Outbreaks of the disease were reported for many places in southwestern Germany, Bohemia, the Alsace region in nowadays France, Switzerland, and Italy. Common graves with massive numbers of human bones at the cemetery of St. Michael Church and the cemetery on the estate of the Dominican order near nowadays Waisenhausplatz found during the last century may indicate that hundreds of citizens became the victims of the plague. There are indications that a fraternity for taking care of the sick and removing the bodies of the deceased from houses was formed in 1501, whose members later on stayed together and became known as the choral society Singergesellschaft, which is still active today as the Loebliche Singergesellschaft of 1501. (They are probably one of the oldest clubs in Europe).
1520s: The ideas of the protestant religious movement advanced by Martin Luther spread rapidly in Pforzheim. Its most prominent promoters were Johannes Schwebel, a preacher at Holy Ghost church (Heiliggeistkirche), and Johannes Unger, the principal of the Dominican Latin school.
1535–1565: Due to the heritage division of the clan of the Margraves of Baden, Margrave Ernst of Baden made Pforzheim the residential town of his family line. He decided to use the Schlosskirche St. Michael as the entombment site for his family line.
1549: A large fire caused severe damage to the town.
1556: After the conclusion of the Peace of Augsburg in 1555, Margrave Karl II introduced Lutherism (protestantism) as the state religion in the district Baden-Durlach, which included Pforzheim. The (Catholic) monasteries were gradually shut down.
1565: Margrave Karl II chose Durlach as the new residential town. Pforzheim stayed one of the administrative centers of Baden.
1618: At the beginning of the Thirty Years War, the number of inhabitants of Pforzheim is estimated to have been between 2500 and 3000. This was the largest town among all towns in Baden, even though at that time it had already declined somewhat.
1645: Toward the end of the Thirty Years War the "old town" was burned down by Bavarian (i.e. Catholic) troops. It was rebuilt, but without the former fortifications, which gave it the status of a village-like settlement. It soon vanished from historical records. The "new town" had survived.
1688–1697: The "War of the Palatinian Succession" (also called the Nine Years War) caused tremendous destruction in Southwestern Germany. The French "sun king" Louis XIVs efforts to expand the territory of France up to the Upper Rhine river and to put the Elector Palatine under pressure to severe its ties with the League of Augsburg included the Brulez le Palatinat! tactics of destroying major towns on both sides of the Rhine river. These tactics seem to have been mainly the idea of the French war minister, Francois Michel le Tellier, Marquis de Louvois.
Pforzheim was occupied by French troops on October 10, 1688. Commanding officer is said to have been Joseph de Montclar. The town was forced to accommodate a large number of soldiers and had to pay a large amount of "contributions" to the French. When the army unit was about to depart early in the morning of January 21, 1689 (obviously because an army of the Holy Roman Empire had been approaching), they set many major buildings on fire, including the palais, the city hall, and vicarages. About 70 houses (i.e. one quarter of all houses) and part of the towns fortifications were reportedly destroyed.
Between August 2 and August 4, the French army under the general command of Marshal Jacques Henri de Durfort de Duras again crossed the Rhine river and began the destruction of major towns in Baden. On August 10, 1689, a French army unit under the command of General Ezechiel du Mas, Comte de Melac appeared in front of Pforzheims town gates, but this time the town refused to surrender. In response, the French army began shelling the town with cannons from the Rod hill located southwest of the town, and the several hundred soldiers of the German imperial command, who were defending the town, were forced to surrender. After a short period of looting, the French troops set the inner town area on fire on August 15, which made that area uninhabitable for several weeks. Then the French moved on.
During the following two years, French troops stayed away from Pforzheim, but the economic situation of the town was miserable. In addition to this, the reconstruction of the town and the repairs of the fortifications under the supervision of Johann Matthaeus Faulhaber, the chief construction officer of the Margraviate Baden, required a lot of efforts. The accommodation of an imperial garrison under the command of (then) colonel Count Palfy also was a heavy burden.
In 1691, Louvois instructed his marshals to destroy those towns which were to serve as winter quarters for imperial troops, explicitly including Pforzheim, and then continue to Wuerttemberg for further destructions. After the French troops had crossed the Rhine river under the command of Marshal Guy Aldonce de Durfort de Lorges at Philippsburg on August 3, 1691, they assaulted the Margraves residential town of Durlach and 1,200 cavalry men, 300 dragoons and 1,200 infantry men advanced toward Pforzheim where they arrived in the morning on August 9 and surrounded the town. When the approximately 200 imperial soldiers under the command of Captain Zickwolf and other men in the town refused to surrender, the siege began. After shelling the town during the day and the following night, the resistance of the town broke down and on August 10 in the morning the French forced the town gates open, occupied and looted it (although with little success, as there was not much left to be taken away). On August 12, the French moved on, this time refraining from setting houses on fire. The fortification had again been damaged, though (the White Tower, the Auer Bridge Gate, the Upper Mill and the Nonnen Mill were burnt down). The French also stole all church bells, except for one minor one.
On September 20, 1692, again crossed the Rhine river under the general command of Marshal Guy Aldonce de Durfort de Lorges, and advanced toward Durlach and Pforzheim. On September 24, 2,000 cavalry soldiers and 1,200 infantry and artillery troops under the command of Marshal Noel Bouton de Chamilly, moved to Pforzheim, where the town and 600 soldiers of the imperial German army in town surrendered without any military engagements. The rest of the French army arrived on September 27 under the command of Marshal de Lorges. On the same day, the French army moved on to Oetisheim near Muhlacker and attacked an imperial army unit of 4,000 cavalry men under the command of Duke Frederick Charles of Wurttemberg-Winnental in their camp. As they were taken by surprise, they withdrew hastily and lost several hundred men, either killed or captured by the French. (The Duke himself was among the French prisoners.) On September 28, the French army returned to Pforzheim and established a camp. It was reported that the entire Enz valley between the village of Eutingen east of Pforzheim and the village of Birkenfeld west of Pforzheim was occupied by the 30,000 French soldiers camps. From their base in Pforzheim, French army units obviously under the leadership of Marshal de Chamilly advanced along the river valleys of Nagold and Wuerm and looted and destroyed the villages and towns of Huchenfeld, Calw, Hirsau, Liebenzell and Zavelstein. They also destroyed Liebeneck castle about 10 kilometers from Pforzheim towering above the Wuerm valley, where part of the Pforzheim town archives were hidden. The archive was burned. Another part of the town archive as well as documents of Baden administrative office had been brought to Calw, were they went up in flames, too.
When the French troops left after about one week of occupation, they again looted Pforzheim and put it on fire. This time, all houses which had survived the two previous fires, were destroyed. In the Au suburb, only three houses survived. The Au bridge was heavily damaged. Only four houses survived in the Broetzingen suburb. The town church St. Stephan and a large part of the Dominican monastery complex were also destroyed. The Castle Church (Schlosskirche) St. Michael was heavily damaged, and the family tombs of the Baden Margraves in the church were ravaged by the soldiers. The last remaining church bell and the churches clockworks were stolen as well. The town wall was damaged again, including the town gates. After the one-week presence of 30,000 soldiers in a town of only a few thousand citizens, all food was gone, including the seeds saved for next springs sowing season. Every tree and grapevine on the valley slopes had been used up as firewood. The French army reached their camp in Philippsburg on October 5, 1692.
Pforzheim is one of the regional centers (Oberzentrum) in Baden-Wurttemberg and has one of the highest densities of industrial activity in the state.