It then continues towards Jefferson Hills in the northwest, where it meets the northern terminus of Pennsylvania Route 43 (Mon-Fayette Expressway) at exit 54. PA 43 is expected to extend further north of PA 51. Northwest of PA 43, PA 51 becomes Clairton Boulevard.
The road then travels towards Jefferson Hills in the northwest, reaching its northern terminus at Pennsylvania Route 43 (Mon-Fayette Expressway) at exit 54.  PA 43 is expected to continue northward from this point. Northwest of PA 43, PA 51 becomes Clairton Boulevard.