Pennsylvania began automobile registration in 1903.  The first state-issued plates, issued annually from 1906 through 1909, were actually operator's license plates.  In 1910, true registration plates started, with the 1910-15 issues displaying an aluminum keystone-shaped tab.  Pennsylvania plates have traditionally featured keystones, the state map outline, or both over the years, but a major exception was the 1971-76 Bicentennial issue depicting the Liberty Bell.  The earliest of the two currently valid base plates began issue in 1999.