Pittsfield is a city in Pike County, Illinois, United States. The population was 4,211 at the 2000 census.
The city was named after Pittsfield, Massachusetts. It is the county seat of Pike County. It was home to John Hay, Lincoln's personal secretary, ambassador to England under President William McKinley, later Secretary of State for Theodore Roosevelt and creator of the Open Door Policy in China. As county seat, the town was one of the various places in central Illinois where Abraham Lincoln practiced law as part of the circuit court, working on 34 cases between 1839 and 1852. One local newspaper, now known as the Pike Press, was then owned by another of Lincoln's future secretaries, John Nicolay, and featured an editorial containing one of the first known suggestions of Lincoln as the Republican nominee for the presidency.
Pittsfield is the self-proclaimed "Pork Capital" of the Midwest, owing to the long history of pork production in the region, which fed into the large meat-packing industry of Chicago. Though agriculture in the region is no longer so dependent on pork, the town still hosts a yearly "Pig Days" festival.