Frederick to Thurmont
The Potomac Edison was an electric interurban that was originally known as the Hagerstown & Frederick. In addition to the line featured here, there was also a line from Frederick to Hagerstown, with branches to Boonsboro and Jefferson. Most of the lines were abandoned during the depression. (Potomac Edison is a unit of Allegheny Power.)
This line travels mostly through what is now private property, through farms and open land in north central Maryland. The right-of-way is easily seen from a distance, as it is still used by Alleghany Power for electric transmission lines.
Heading north from Frederick, the line passed through Yellow Springs, Bethel, Locust Grove, Lake View, Lewistown, Creagerstown, Catoctin, Red Hill and Thurmont, where it interchanged with the Western Maryland (now Maryland Midland). In Thurmont, a paved trail follows the right-of-way for a mile or so through town.
In addition to the H&F lines mentioned on this entry, the H&F also had a line that left Hagerstown and went north to the Pennsylvania border at Spring Grove. It was part of the original Hagerstown Railroad and it interchanged passengers with the Chambersburg, Greencastle and Waynesboro Railroad at Spring Grove, PA. It was not a physical connection to that railroad however.
You should really consider creating a Hagerstown & Frederick Railroad entry for this site to include all of the H&F lines that were abandoned. In addition to the two mentioned herein, there were lines from Frederick to Hagerstown up over South Mountain through Middletown. There was a lines to Williamsport, Boonsboro, and Jefferson.