Human settlement in the Tonghua area dates from about 6000 years ago. In the Western Han Dynasty, Tonghua belonged to the Liaodong Fourth Commandery (遼東四郡). Under the Japanese occupation of Manchuria after 1932, a railway was constructed linking Tonghua with the main Manchurian rail network and with northern Korea. In 1985, Tonghua became a prefecture-level city under the approval of the State Council.
The city has a recent record of extreme violence including Shosankoku incident in 1945, Tonghua Incident in 1946 and Tonghua Iron and Steel Group riot in 2009.
Tonghua has a monsoon-influenced, humid continental climate (Köppen Dwa), with long, very cold, windy, but dry winters and hot, humid summers; spring and autumn are brief. The monthly 24-hour average temperature ranges from −14.2 °C (6.4 °F) in January to 22.3 °C (72.1 °F) in July; the annual mean is 5.60 °C (42.1 °F). During the warmer months, rainfall is enhanced by the mountainous topography, allowing for a generous annual precipitation total of 870 millimetres (34.3 in). However, the monsoon still means that more than 60% of the annual precipitation falls from June to August alone.
Traditionally, Tonghua occupied a railhub position in a region of China noted for trade in only three agricultural commodities. These were ginseng, marten furs and deer antler products. In the 1980s Tonghua had some success with a wine distillery producing sweet, sticky red wines that proved popular with local consumers. From 1987 onwards a bienniel wine festival was inaugurated, but this and the industry it promoted ultimately failed commercially owing to competition with joint-venture wine companies such as Dragon, who were able to produce a product that was marketable overseas. Following this failure, Tonghua industry was thrown back on its traditional agricultural products - and a few small but viable factories, including one specialising in artificial furs.
A fledgling tourist trade sought to highlight Tonghua attractions such as some impressive ski slopes, the tomb of the local hero General Yang (a resister to the Japanese occupation of Manchukuo in the 1930s) and the beautiful Changbai Shan Nature Reserve for which Tonghua serves as a connecting railway station from the major population centres to the north and west.
Tonghua's population hovers around 300,000, but census information is difficult to assess as it includes demographic information from other towns nearby (for example, Erdaojiang - a suburb of Tonghua, and even Hunjiang, a city to the east). The inclusion of these suburbs and surrounding towns greatly swells Tonghua's official population beyond the 300,000-mark.
Poor, backward and, at local level, conservatively led, Tonghua was late in benefiting from the economic reforms (gai ge) of national leaders such as Zhao Ziyang. Although the railway provided useful direct links to major cities such as Shenyang, Tianjin and Changchun, few signs of progress could be seen on Tonghua's dirty streets until the mid-1990s, when plans were approved for a plethora of building projects which transformed the city. These have helped fuel a resurgence in Tonghua's commercial strength. Now, however, significant improvements can be seen and the city is dotted with shops and shopping centers all around.
Erdaojiang District has a number of steelworks, and tens of thousands of steelworkers are employed locally. In July 2009, workers at Tonghua Iron and Steel Group rioted (See main article) at news of a takeover deal by privately owned Jianlong Steel, and the general manager of the firm was beaten to death. The unrest reportedly involved 30,000 workers, with up to 100 injured in clashes with police. The takeover was promptly scrapped.
The city of Tonghua has also become a hub for a range of Chinese pharmaceutical firms, including domestic insulin producer Tonghua Dongbao Pharmaceuticals Ltd. These companies are generally spread among the various "Industrial parks" found throughout the city, with 46 projects located in these parks in 2012 alone. Investment in Tonghua's pharmaceutical industry is on the increase, with 27 of these projects worth over 100 million Yuan. Other pharmaceutical producers in the area include Jingma, Zhenghe and Wantong Pharmaceuticals.
Railways from Shenyang to Jilin and Meihekou to Ji'an meets in Tonghua. Trains from Tonghua Railway Station connect the city with Beijing, Qingdao, Shenyang, Dalian and several other major cities in China.
Tonghua is served by G11 Hegang-Dalian Expressway.