During the American Revolution, it was the site of the First and Second Continental Congresses. After the Revolution, the city was chosen to be the temporary capital of the United States from 1790–1800.
At the beginning of the 19th century, the federal and state governments left Philadelphia, but the city continued for some years to be the country's cultural and financial center. Its large free black community aided fugitive slaves and founded the first independent black denomination in the nation, the African Methodist Episcopal Church. Philadelphia became one of the first U.S. industrial centers with a variety of industries, the largest being textiles. It had many economic and family ties to the South, with southern planters maintaining second homes in the city and having business connections with banks, sending their daughters to French finishing schools run by refugees from Saint-Domingue (Haiti), selling their cotton to textile manufacturers, which in turn sold some products to the South, for instance, clothing for slaves. At the beginning of the American Civil War, there were many southern sympathizers, although most city residents became firmly Union as the war went on.
After the American Civil War, city government was controlled by the Republican Party; it established a political machine that gained power through patronage. By the beginning of the 20th century, Philadelphia was described as "corrupt and contented." Various reform efforts slowly changed city government; in 1950, a new city charter strengthened the position of mayor and weakened the Philadelphia City Council. Beginning during the Great Depression, voters changed from traditional support for the Republican Party to increasing support for the Democratic Party of President Franklin D. Roosevelt, which has now been predominant in local politics for many decades.
https://en.wikipedia.org/wiki/History_of_Philadelphia