| State: | PA |
| Type: | PA |
| Route: | 173 |
| Length Mi: | 45.7 |
| Length Round: | 1 |
| Map Custom: | yes |
| Direction A: | South |
| Terminus A: | near Slippery Rock |
| Junction: | near Grove City |
| Direction B: | North |
| Terminus B: | near Cochranton |
| Counties: | Butler, Mercer, Crawford |
| Previous Type: | PA 1926 |
| Previous Route: | 172 |
| Next Type: | PA |
| Next Route: | 174 |
Pennsylvania Route 173 (PA 173) is 45.7-mile-long (73.5 km) state highway located in western Pennsylvania, running from PA Route 8 south of Slippery Rock in Butler County, to PA Route 27 north of Cochranton in Crawford County.
PA 173 is designated as part of Washington’s Trail between its southern terminus at PA Route 8 and Slippery Rock.
From the village of Stone House at PA Route 8, PA 173 heads north-northeast in Butler County about 4miles to the borough of Slippery Rock, home to Slippery Rock University. Near the north end of town, the route intersects with PA 108 at the southern terminus of PA Route 258. Routes 108 and 173 overlap, traveling northeasterly for 0.3miles, where the concurrency ends and PA 173 turns northward. About 3miles later, the route crosses the county line.
After entering Mercer County, PA 173 continues northerly almost 3.5miles to the borough of Grove City, the site of Wendall August Forge and Grove City College. The route intersects with PA Route 58, and the two overlap northeastward 0.2miles. This concurrency ends at the intersection of PA Route 208, where Routes 173 and 208 concurrency northward – for about 0.33miles, the northbound and southbound lanes run on parallel one-way streets through the downtown area. About 0.4miles later, the concurrency ends, PA 173 continues north, and leaves the borough. The route interchanges with I-80 about 2.5miles later, and then intersects with PA Route 965 about 6miles after that at the village of Perrine’s Corners.
PA 173 enters the borough of Sandy Lake 4miles later, where it forms a brief concurrency with US 62; the concurrency ends at the eastern terminus of PA Route 358. PA 173 leaves the borough, and just over 4miles later, intersects with Georgetown Rd., which is the former alignment of PA Route 285 in the borough of New Lebanon. The route passes through the village of Milledgeville 4miles north, and then crosses the county line just over 1miles after that.
A little more than 2miles after entering Crawford County, PA 173 turns northeasterly as it intersects with the eastern terminus of PA Route 285, and then enters the borough of Cochranton shortly thereafter. In Cochranton, the route intersects with the former alignment of US 322, and then 0.6miles later, after leaving the borough, it intersects with the current alignment of US 322. Not quite 2miles later, the route passes through the village of Kasters Corners, and then runs another 5miles before its northern terminus at PA Route 27.
In 1926, the segment from Stone House to Slippery Rock was designated as PA 8. In 1941, the entire alignment was designated as PA 78 before receiving the current number in 1961.[1]