Wikipedia:WikiProject U.S. Roads/Pennsylvania/Selected article/December 2010

Pennsylvania Route 646 (designated by the Pennsylvania Department of Transportation as SR 0646) is a 19.09 miles (30.72 km) long state highway located in McKean county in Pennsylvania. The southern terminus is at PA 59 in Keating Township. The northern terminus is the New York state line in Foster Township. The route continues as New York State Route 16 in Cattaugarus County.

Route 646 was assigned in the 1928 mass numbering of state routes in Pennsylvania. At that time, it consisted entirely of the PA 346–state line stretch in Foster Township. The rest of the stretch consisted of Route 59, now realigned, and Route 746, now decommissioned. Route 746 was decommissioned in 1946, and PA 59 was realigned in 1952, with PA 646 being extended onto its current alignment. The route has remained virtually unchanged since the change in 1952.