|Maintained by PennDOT|
|Length||4.00 mi (6.44 km)|
|South end||US 19 in Mt. Lebanon|
|I-376 / US 22 / US 30 in Green Tree|
|North end||PA 50 in Pittsburgh|
Pennsylvania Route 121 (PA 121) is a 4.00-mile-long (6.44 km) state highway located in Allegheny county in Pennsylvania. The southern terminus is at US 19 in Mt. Lebanon. The northern terminus is at PA 50 on the border of Greentree and the Pittsburgh neighborhood of Westwood.
PA 121 begins at an intersection with US 19 in Mt. Lebanon, heading northwest on Cochran Road, a two-lane undivided road that heads through residential areas. From the southern terminus, the route is concurrent with the Yellow Belt of the Pittsburgh/Allegheny County Belt System. The road widens to four lanes as it enters commercial areas and becomes the border between Mt. Lebanon to the southwest and Scott Township to the northeast. PA 121 splits from the Yellow Belt and Cochran Road by turning north onto four-lane Greentree Road, fully entering Scott Township. The road passes through residential and commercial areas as it turns to the northeast, narrowing to two lanes as it enters Green Tree. In this area, the route passes more homes, with the Blue Belt joining the road at the Potomac Avenue intersection. PA 121 curves to the north, becoming a three lane road with a reversible lane. The road enters commercial areas, widening to four lanes as it reaches an interchange with I-376/US 22/US 30. Immediately after this interchange, PA 121 turns west onto Mansfield Avenue, a three lane road with one northbound lane and two southbound lanes. The route turns north onto two-lane Poplar Street and heads into wooded areas of homes. PA 121 heads northwest to reach its northern terminus at PA 50 on the border of Green Tree and Pittsburgh in commercial areas.
The original PA 121 ran from East Waynesburg to Point Marion in Greene County from 1928 to 1950. In 1961, PA 121 was reactivated and reassigned to its current route. From 1940 to 1946, the Greentree Road segment of the present-day PA 121 from Cochran Road to Mansfield Avenue was designated as PA 802.
The entire route is in Allegheny County.
|Mt. Lebanon||0.00||0.00||US 19 / Yellow Belt (Beverly Road / Cochran Road)||Southern terminus of PA 121; southern end of concurrency with Yellow Belt|
|0.70||1.13||Yellow Belt (Greentree Road) to PA 50 – Heidelberg||Northern terminus of Yellow Belt concurrency|
|Scott Township||1.14||1.83||To I-376 / US 22 / US 30 / Forsythe Road – Carnegie|
|Green Tree||2.20||3.54||Blue Belt (Potomac Avenue)||Southern terminus of Blue Belt concurrency|
|3.18||5.12||I-376 / US 22 / US 30 (Penn-Lincoln Parkway) – Pittsburgh International Airport, Pittsburgh||Exit 67 (I-376); no access from PA 121 south to I-376 / US 22 / US 30|
|3.19||5.13||Greentree Road – West End|
|3.39||5.46||To I-376 / US 22 / US 30 / Mansfield Avenue / Poplar Street|
|Pittsburgh||4.00||6.44||PA 50 / Blue Belt (Noblestown Road)||Northern terminus of PA 121; northern terminus of concurrency with Blue Belt|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi|
- "Pennsylvania state roads". Pennsylvania Spatial Data Access. Pennsylvania Department of Transportation. 2012. Retrieved December 24, 2012.
- Google (March 2, 2011). "overview of Pennsylvania Route 121" (Map). Google Maps. Google. Retrieved March 2, 2011.
- Allegheny County, Pennsylvania Highway Map (PDF) (Map). PennDOT. 2011. Archived from the original (PDF) on July 20, 2011. Retrieved March 2, 2011.
- "PennDOT VideoLog - Allegheny County - Route 0121". Pennsylvania Department of Transportation. October 7, 2011. Retrieved December 27, 2012.