Sidling Hill Road Cut, Maryland Sidling Hill Road Cut, As Seen From Pedestrian Bridge. Southern Maryland. Sidling Hill Also Sits in Southern Pennsylvania. Allegheny Mountains & Appalachian Mountains. (Photo: Jenny Gaffron Woytek)Although this section of Route 40 & I68 belongs to Maryland, we have used this highway to travel from Western Pennsylvania to Central Pennsylvania as an alternative to the PA Turnpike. February 15, 2020. Fun fact: Route 40 was built in the early 1800’s as the National Road.