Joe Biden is the projected president-elect as the Associated Press calls Pennsylvania for the former vice president.
The crowd outside the Pennsylvania Statehouse doubled after the news was announced.
Several rallies for both sides were held on the steps even before the race was called.
The vote was close in the swing states, including in Pennsylvania. The popular vote was not close, as Biden had a commanding lead.
President-elect Biden urged national unity in a statement Saturday afternoon.
Several elected officials sent messages to Biden and Vice President-elect Kamala Harris, the first woman and woman of color elected to the White House.