 When routes were first legislated in Pennsylvania in 1911, present-day PA 999 was not given a legislative number.By 1926, the road connecting Millersville to Lancaster was paved.PA 999 was designated in 1928 to run from Millersville northeast to US 30/PA 1 (now PA 462) in Lancaster, heading east on Frederick Street, north on George Street, and northeast along its current alignment.