PA 519 begins at an intersection with US 40 in the community of Glyde in North Bethlehem Township, heading north on a two-lane undivided road. The route passes through wooded areas with some farms and development, crossing into Somerset Township and reaching an interchange with I-70. Past this interchange, the road runs through more rural areas before reaching the community of Eighty Four. Here, the road passes homes and businesses as it comes to an intersection with PA 136. After this intersection, PA 519 heads into North Strabane Township and passes areas of commercial development a short distance to the east of an Allegheny Valley Railroad/CSX line, running through Wylandville. The route curves northeast into areas of farms before turning northwest and passing through the residential community of Gambles. The road crosses the Allegheny Valley Railroad/CSX line and continues northwest through farmland and woodland with some residential development. PA 519 reaches an interchange with US 19 and comes to an intersection with PA 980 a short distance later.
At this point, the route turns to the west near areas of residential and commercial development, coming to an interchange with I-79. The road becomes Hill Church Houston Road here and heads northwest through commercial areas, crossing the Pittsburgh and Ohio Central Railroad and Chartiers Creek. After the latter, PA 519 enters Houston and becomes South Main Street, passing homes and businesses. In the commercial center of Houston, the route briefly turns south onto West Pine Street before heading west on Western Avenue past more residences. The road forms the border between Houston to the north and Chartiers Township to the south before fully entering Chartiers Township. PA 519 continues northwest through areas of farmland and woodland with occasional residential and commercial development, passing through McConnells Mills and Export. The road turns more to the north and enters forested areas, heading into Mount Pleasant Township. The route passes through the residential community of Westland and comes into a mix of farm fields and woods. PA 519 turns northwest and reaches its northern terminus at PA 50.
From 1936 to 1941, the original PA 519 began at the intersection of Saw Mill Run Blvd. and West Liberty Ave. and ran southbound to U.S. 19 in Morganza. In 1941, PA 519 was "swapped" with what was U.S. 19 at that time, running from Canonsburg to Crafton. In 1947, the southern terminus of PA 519 moved from Morganza Rd. in Canonsburg to its current terminus at U.S. 40 in Glyde. In 1954, the northern terminus was moved from Noblestown Rd. in Crafton Heights to the intersection of Washington Ave. and Miller's Run Rd. in South Fayette Township. In 1972, the northern terminus was moved one last time to its current location at PA 50 in Hickory.