Pittsburg, the county seat of Camp County, is at the junctions of U.S. Highway 271 and State Highway 11 and of the Louisiana and Arkansas and the St. Louis Southwestern railways, sixty miles southwest of Texarkana in the central portion of the county. It is the largest and the oldest town in the county. There are six major lakes within eighteen miles of Pittsburg that are reputed to be among the best bass-fishing lakes in Texas. Caddo and Cherokee Indians resided in the area during the early 1800s, but they had for the most part abandoned the area before settlers began arriving from Georgia, Tennessee, and Alabama in the late 1830s. A community began to emerge in the 1850s, and when the post office was established in 1855 it was named Pittsburgh, in honor of the family of William Harrison Pitts, said to have arrived from Warren County, Georgia, the year before. The Pittsburg Gazette was founded in 1884 and has been in continuous operation since that time. In 1893 the spelling of the post office name was changed to Pittsburg. As the part of Upshur County near Big Cypress Creek became more heavily populated, Pittsburg grew in size and importance. The roads between there and Gilmer, the county seat and major market center of Upshur County, were of poor quality, and Big Cypress Creek was often difficult to cross during rainy seasons. Thus by 1860 Pittsburg became the major market center for the future Camp County. The town had doctors, lawyers, a watchmaker, a brick mason, two shoemakers, two blacksmiths, and several merchants, carpenters, and wagonmakers, as well as a Methodist church. By 1870 Pittsburg served as the post office for 2,400 people.
When Camp County was organized in 1874, Pittsburg was one of three towns proposed for the county seat. As the largest and most centrally located settlement, it defeated Leesburg and Center Point, receiving 500 of the 797 votes cast. The new courthouse, which was constructed on land donated by William H. Pitts, was built with bricks that had been manufactured in Pittsburg. During the late 1870s the East Line and Red River Railroad was constructed across the county from east to west, and the Texas and St. Louis Railway was constructed across the county from north to south. The two railroads came through Pittsburg, increasing both its importance as a trade center and the size of the area it served. By 1890 Pittsburg had a population of 1,203. On August 21, 1891, an election resulted in favor of incorporation, 110 to 74, and E. A. King was elected the first mayor. An 1896 description of Pittsburg concluded that the city was an "exceptionally desirable location for factories" because of its rail connections and the quantity of timber available. From the early years Pittsburg had sawmills, wagonmakers, and builders. By 1896 the town also had a foundry, a tannery, an ice factory, and a bottling works. Still, the town remained primarily a supply and shipping point for farmers well into the twentieth century. As late as 1940 there were only 242 individuals involved in manufacturing all of Camp County.
The most remarkable manufacturing enterprise in Pittsburg involved an early flying machine. Around 1901 Burrell B. Cannon, a local mechanic and part-time minister, built an aircraft, basing his design on a description in the book of Ezekiel. Twenty thousand dollars' worth of stock was offered in the Ezekiel Airship Manufacturing Company. Cannon had a solid reputation as a mechanic, which inspired the townspeople's confidence in his project. There is debate as to whether the craft ever actually got off the ground; some residents later recalled having seen it lift off for a few feet. Eventually Cannon put the aircraft on a railroad flatcar to ship it to St. Louis, possibly in hopes of interesting investors. The machine was destroyed by a storm, however, while it sat on the tracks in Texarkana. Cannon reportedly built a second model of the aircraft in Chicago in 1913, but the machine crashed into a telephone pole after a brief flight. Cannon returned to Texas and died in Longview in 1922.
In 1897 a privately owned electric generator was constructed in Pittsburg that provided sixteen kilowatts of electricity, enough for lights only. In 1899 a franchise was granted to Southwest Telegraph and Telephone Company to build a telephone system. By 1925 the city had also constructed a municipally owned water and sewer system. By 1900 it had a library. In 1899 residents of Pittsburg had secured a promise of $5,000 from Andrew Carnegie, provided that the city fund a building and agree to maintain the library. The city council matched the $5,000 grant, and a Carnegie Library was constructed. It is reputed to have been the first of the Carnegie libraries in Texas. The library building, which also housed the city hall and a community auditorium, burned in December 1939. A new town library was not constructed until the 1970s.
From 1890 through 1980 each census recorded a larger population for Pittsburg. Beginning in the 1940s, however, the relationship between the town and the remainder of the county began to change. Until the late 1930s the town was primarily a supply center for area farmers. Beginning in the late 1930s or early 1940s, it became more heavily dependent on industry, retail goods, and services provided to its own residents. Between 1940 and 1960 the population of the county fell from 10,285 to 7,849, while the population of Pittsburg increased from 2,916 to 3,796. Thus by 1960 almost half the population of the county lived in Pittsburg. In 1980 Pittsburg had a population of 4,245. In 1988 the town had 107 rated businesses, at least twenty-two of which were industrial concerns. In 1990 the population of Pittsburg was 4,007. The population was 4,347 in 2000.