Shariff Mohammed Kabungsuwan of Johore introduced Islam in the area at the end of the 15th century. He subsequently married a local princess from the Maranao Tribe of Malabang and Maguindanao Province, and established the Sultanate of Maguindanao. The Cotabato Valley formed the sultanate's heartland but its influence extended from the Zamboanga Peninsula to Sarangani Bay and Davao.
The Spaniards launched expeditions to subdue the area throughout the colonial era but they never gained control of the region until the middle of the 19th century after the Spaniards established a military post at what is now Barangay Tamontaka, one of the earliest Christian settlements founded south of the Philippines, in present-day Cotabato City. Spaniards already took with them Chabacanos and Chabacano-speaking Muslims from Zamboanga and Basilan and Cebuanos. Chabacanos being brought by Spaniards are the reason of existing Chabacano dialect in Cotabato City called Cotabateño, evolved from Zamboangueño.
The historical province of Cotabato covered the present area of Maguindanao. In 1903, the American colonial government established the Moro Province and made Cotabato as one of its districts. Upon the conversion of the Moro Province into the Department of Mindanao and Sulu in 1914, the districts were made into provinces.
In 1942, the Japanese Imperial forces entered what is now Maguindanao.
In 1945, Maguindanao was liberated by allied Philippine Commonwealth troops and Maguindanaoan guerrilla units after defeating the Japanese Imperial forces in the Battle of Maguindanao during the Second World War.
The territory of the old province of Cotabato was reduced in 1966 when several of its municipalities were separated from it and constituted into the newly created province of South Cotabato. In 1973, Cotabato was dissolved when it was split to create three new provinces: Maguindanao, (North) Cotabato and Sultan Kudarat.
Maguindanao is the only Muslim-majority province of the four created out of the original Cotabato Province. In 1989, majority of its voters opted to join the Autonomous Region in Muslim Mindanao but Cotabato City did not, which, ironically, has since served as the provisional capital of the Autonomous Region in Muslim Mindanao (ARMM).
On October 31, 2006, Maguindanao voters approved the creation of a new province to be composed of 10 towns from the province. Of more than 500,000 voters registered, 285,372 favored the creation of the province, and 8,802 voted against it. The new province, Shariff Kabunsuan, established through Muslim Mindanao Autonomy Act No. 201 by the ARMM Regional Legislative Assembly, became the country's 80th province and the 6th in the ARMM. It was composed of the towns of Datu Odin Sinsuat, Kabuntalan, Upi, Sultan Kudarat, Datu Blah T. Sinsuat, Sultan Mastura, Parang, Buldon, Matanog and Barira. However, in July 2008, the Supreme Court, in an 8-6 vote, nullified the province's creation, restoring its municipalities to Maguindanao, ruling that "Only Congress can create provinces and cities because the creation of provinces and cities necessarily includes the creation of legislative districts".
On November 23, 2009, a 2010 gubernatorial election caravan supporting Esmael Mangudadatu, vice mayor of Buluan, was attacked. Fifty-seven people were killed, including Mangudadatu's wife and sisters, supporters, local journalists, and bystanders. On December 4, 2009, a number of homes belonging to the Ampatuan political family were raided in connection with the massacre.
President Gloria Macapagal Arroyo officially declared martial law in the province of Maguindanao on December 5, 2009, Saturday morning.
In a press conference past 7 am, Executive Secretary Eduardo Ermita announced Proclamation No. 1959 declaring a state of martial law and suspending the privilege of the writ of habeas corpus in the province of Maguindanao, except for certain areas identified as bailiwicks of the Moro Islamic Liberation Front (MILF) separatists.
The declaration of martial law led to the "arrests without warrants" of other members of the Ampatuan clan who have been linked to the November 23 massacre of 58 civilians.
On August 15, 2011, Mangudadatu and his convoy were ambushed as they were on their way to his birthday celebration.
On January 25, 2015, 44 members of the Special Action Force were killed after they killed the Jemaah Islamiyah terrorist Zulkifli Abdhir aka Marwan, by allegedly Moro Islamic Liberation Front and Bangsamoro Islamic Freedom Fighters in Mamasapano, Maguindanao.
On February 2016, Maguindanao experienced the effects of the 2014–16 El Niño, causing destruction on rice and corn fields due to drought. The province declared a state of calamity in response to the damages caused.
Maguindanao is situated in the central section of Mindanao, bordered by Lanao del Sur to the north, Cotabato to the east, Sultan Kudarat to the south, and the Illana Bay to the west.
Maguindanao comprises 36 municipalities, further subdivided into 508 barangays. Cotabato City, although geographically grouped with Maguindanao, is administratively independent from the province as well as from the ARMM.
The province is divided into two congressional districts. In October 2006, the first congressional district was split off into a new province, Shariff Kabunsuan. However, the ARMM's Act creating the province was nullified by the Supreme Court in July 2008, on the basis that creation of a province is a function of the Philippine legislature. The area has since reverted to the province of Maguindanao.
House Bill No. 5185 was introduced in the House of Representatives on March 2, 2017 by third-term Representative Bai Sandra Sema who is barred by law to run for another term in her current district in 2019. It seeks to establish a new province called Maguindanao North, consisting of 13 municipalities, of which Datu Odin Sinsuat will be the designated capital. The independent city of Cotabato will be grouped with the proposed province only for the purposes of congressional representation. The creation of the new legislative district of Maguindanao North will allow Rep. Sema to once again run for office in a technically different district.
The population of Maguindanao in the 2015 census was 1,173,933 people. When Cotabato City is included for geographical purposes, the province's population is 1,473,371 people.
The majority of people in Maguindanao are the Maguindanao, with some Cebuanos, Hiligaynons, Chavacanos, Tausugs, Yakan, and Bajau.
The main language is Maguindanao. Cebuano, Hiligaynon and Chavacano are also spoken by both, Christians and Muslims. The dialect of Chavacano native to Cotabato City is called Cotabateño, which evolved from the Zamboangueño dialect. Also spoken are Tagalog, as well as English and Arabic.
Maguindanao inhabitants are predominantly practitioners of Islam, majority of which are Sunnites, with a minority of Christians, (mostly Roman Catholics) who are mostly Cebuanos, Ilonggos and Chavacanos. Roman Catholics of Maguindanao fall under the jurisdiction of the Roman Catholic Diocese of Kidapawan, a suffragan of the Archdiocese of Cotabato. Iglesia ni Cristo (INC) has several locales in Maguindanao.
Maguindanao is divided into two congressional districts, which elect members to the House of Representatives. For the brief period that the province of Shariff Kabunsuan existed, Maguindanao became a lone-district province. Since the appointment of a new set of provincial officials for the reunified province of Maguindanao by the ARMM Governor in January 2009, the provincial government has reverted to the Sangguniang Panlalawigan district configuration from before Shariff Kabunsuan was created.
Having elected to join the Autonomous Region in Muslim Mindanao (ARMM), Maguindanao also sends six representatives (three per SP district) to the ARMM Regional Legislative Assembly that convenes in Cotabato City.
When the province was established in 1973, the designated seat of government was the municipality of Maganoy. The first appointed governor, Simeon Datumanong, held office in Limpongo, a former barangay in Maganoy which is now part of the municipality of Datu Hoffer Ampatuan.
Datumanong's successor Zacaria Candao, on the other hand, held office at P.C. Hill, the site of the former headquarters of the Philippine Constabulary in Cotabato City, an autonomous chartered city not under Maguindanao's provincial jurisdiction.
In 1977 following the resignation of Candao, President Ferdinand Marcos moved the province's seat of government to the municipality of Sultan Kudarat (hometown of the newly-appointed governor Sanggacala Baraguir) by virtue of Presidential Decree No. 1170. During his term Baraguir held office at the then-newly-constructed provincial capitol in that municipality's Brgy. Simuay Crossing.
The next governor, Sandiale Sambolawan, held office in his hometown of Maganoy following his election to the governorship in 1980. In an attempt to legitimize the restoration of Maganoy's status as the seat of provincial government, Batas Pambansa Blg. 211 was enacted in 1982, but with the explicit provision that the change will only take effect after a plebiscite affirms the transfer. A plebiscite was scheduled for 18 December 1982, but was never administered, thus making the municipality of Sultan Kudarat still capital of Maguindanao by law (de jure), but Maganoy being the capital in practice (de facto). Following the end of the Marcos Regime, the next two governors — Zacaria Candao (1986–1992; 1995–2001) and Norodin Matalam (1992–1995) — both held office in the existing capitol at Sultan Kudarat thereby restoring the municipality's status as both de jure and de facto provincial capital from 1986 to 2001.
Despite the lack of legal justification in the form of a law amending P.D. No. 1170 of 1977 or the passage of a supporting Sangguaniang Panlalawigan (SP) resolution, the next governor, Andal Ampatuan Sr. (governor from 2001–2008), and his successor, son Sajid Ampatuan (2008–2009), held office in the Ampatuan clan stronghold of Shariff Aguak (renamed from Maganoy in 1996), citing security concerns connected to clan rivalry. A new ₱218-million provincial capitol complex, inaugurated in 2009 in the presence of President Gloria Macapagal-Arroyo, was located adjacent to the homes of the Ampatuans, and sat on a piece of Amaptuan clan land that had not been legally deeded to the government. The Ampatuans were even known to spend more time within the "satellite offices" they set up within their private properties, despite though the new capitol being located adjacent to their homes.
Esmael Mangudadatu, who took office after defeating Andal Ampatuan Jr. in the 2010 gubernatorial election, cited security concerns when he decided to work from a "satellite office," named the Rajah Buayan Silongan Peace Center, in his hometown of Buluan; this move was supported by Resolution No. 5, series 2010, of the Sangguniang Panlalawigan (SP) of Maguindanao. SP Resolution No. 78, dated 3 May 2011, further allowed the transfer of the legislative branch of the provincial government (Sangguniang Panlalawigan) to the rehabilitated old capitol site in Brgy. Simuay Crossing, Sultan Kudarat. This effectively made both Buluan and Sultan Kudarat — located 120 kilometers apart by road — the seats of the executive and legislative branches of provincial government respectively.
On 3 April 2012, the SP of Maguindanao issued Resolution No. 132, reiterating that the town of Sultan Kudarat was the capital of Maguindanao. However this was superseded by a new resolution passed in 2014 naming Buluan the new capital of Maguindanao. Buluan's Rajah Buayan Silongan Peace Center now serves as the provisional capitol building, pending the completion of the executive building in the new capitol complex. However, the legislative branch of provincial government, the Sangguniang Panlalawigan of Maguindanao, continues to hold sessions in the rehabilitated buildings of the old provincial capitol in Simuay, Sultan Kudarat.
The Ampatuan-built former provincial capitol complex in Shariff Aguak, initially planned to be converted for public school use, is now set to become the new headquarters of the ARMM's Bureau of Fire Protection.
The native Maguindanaon culture revolves around Kulintang music, a specific type of gong music, found among both Muslim and non-Muslim groups of the Southern Philippines.