Pennsylvania began as a British colony in 1681 when King Charles II appointed William Penn governor. Pennsylvania was the second state admitted to the Union in 1787. The state boundary lines were disputed until 1800. Philadelphia served as the capitol of the United States from 1790 to 1800.
PA-Roots, a non-profit organization, offers free access to its transcribed records projects, including vital records, military records, newspaper articles, obituaries, and county histories of Pennsylvania.
FamilySearch Record Search offers over 25,846 unindexed digital images of Philadelphia marriage records.
Pennsylvania is the only Union state in the Civil War to have an existing file showing names of men who were conscientious objectors for religious reasons. The Genealogical Society of Pennsylvania lists them in a free database.
The Israel Daniel Rupp Collection of 30,000 early Pennsylvania immigrants from 1727-1776 is digitized in PDF form. Get it at the BYU Family History Archives.