1859 – Petroleum is discovered in Titusville, Pennsylvania leading to the world's first commercially successful oil well
. Titusville was a slow-growing community until the 1850s, when petroleum was discovered in the region. Oil was known to exist here, but there was no practical way to extract it. Its main use at that time had been as a medicine for both animals and humans. In the late 1850s Seneca Oil Company (formerly the Pennsylvania Rock Oil Company) sent Col. Edwin L. Drake, to start drilling on a piece of leased land just south of Titusville near what is now Oil Creek State Park. Drake hired a salt well driller, William A. Smith, in the summer of 1859. They had many difficulties, but on August 27 at the site of an oil spring just south of Titusville, they finally drilled a well that could be commercially successful. Teamsters were needed immediately to transport the oil to markets. Transporting methods improved and in 1862 the Oil Creek & Titusville Railroad was built between Titusville and Corry where it was transferred to other, larger east-west lines. In 1865 pipelines were laid directly to the rail line and the demand for teamsters practically ended. The next year the railroad line was extended south to Petroleum Centre and Oil City. The Union City & Titusville Railroad was built in 1865. That line became part of the Philadelphia & Erie Railroad in 1871. That fall, President U. S. Grant visited Titusville to view this important region. Other oil-related businesses quickly exploded on the scene. Eight refineries were built between 1862 and 1868. Drilling tools were needed and several iron works were built. Titusville grew from 250 residents to 10,000 almost overnight and in 1866 it incorporated as a city. In 1871, the first oil exchange in the United States was established here.