It travels northeast and curves to the southeast to cross into Banks County before it leaves town.

It heads to the southeast and meets the northern terminus of SR 323 (John Morris Road) before entering Homer.

At this intersection, the highway begins heading to the northeast taking over the Historic Homer Highway and enters downtown where it intersects Athens Street and Yonah Homer Road, the former of which is an old segment of SR 98.

Then, the route continues to the east, intersecting SR 63 (Martin Bridge Road) in Jewelville, just before entering Franklin County.

In Flat Shoals, to the west-northwest of Hartwell, the route begins a concurrency with SR 77 (Lavonia Highway).

It crosses backwaters of Lake Hartwell before ending at an intersection with Hatton Ford Road and Reed Creek Highway.

[1] The only portion of SR 51 that is part of the National Highway System, a system of routes determined to be the most important for the nation's economy, mobility, and defense, is the entire length of the SR 17 concurrency from Canon to Bowersville.

[14][15] By the middle of 1939, approximately half of the Bowersville–Hartwell segment had a sand clay or top soil surface.

Four segments had a sand clay or top soil surface: from Lula to the southern part of Homer, from the northern part of Homer to the SR 106 intersection south-southwest of Carnesville, from the east end of the SR 145 concurrency south-southeast of Carnesville to Canon, and the northern half of the Hartwell–Reed Creek segment.

Three segments had completed grading, but was not surfaced: from east-northeast of Homer to the SR 59 intersection west-southwest of Carnesville, a portion just east of the east end of the SR 145 concurrency, and the northern part of the Hartwell–Reed Creek segment.

In 1968, it was established and hard surfaced from the SR 51 mainline north and east-northeast to the shore of the "Hartwell Reservoir".