 The road passes over the mountain at an elevation of , which is the highest point on Alt US 40, and was also the highest point along the National Road.East of Negro Mountain, the highway enters Grantsville, where traffic increases, with the AADT increasing to 3,711, the highest traffic density on Alt US 40 in Garrett County.In Grantsville, Alt US 40 meets MD 669, which connects with Pennsylvania Route 669 toward Salisbury, Pennsylvania.