The following highways or routes are numbered 999.
MD 999 (former)
PA 999 
FM 999 | Preceded by 998 | Lists of highways 999 | Succeeded by 1000–1499 |
Pennsylvania Route 999 is a 9.44-mile-long (15.19 km), east–west state highway located in western Lancaster County, Pennsylvania. The western terminus is at PA 441, which has its southern terminus at this intersection, in Washington Boro. The eastern terminus is at PA 462 in Lancaster. PA 999 heads east from Washington Boro to rural areas to Millersville. Upon reaching Millersville, the route heads into developed areas and turns northeast, crossing PA 741. PA 999 continues northeast to its eastern terminus. The route is a two-lane undivided road its entire length. Between Millersville and Lancaster, the route follows a 19th-century private turnpike that runs along the Manor Road that was created in 1742. PA 999 was designated in 1928 between Millersville and U.S. Route 30 /PA 1 in Lancaster. The route was extended west to its current terminus at PA 441 in the 1950s.
