The highway heads northwest, passing the Darien Inland Harbor Campground.

The highway then turns north, traveling through rural areas of the county, until it meets its northern terminus, an intersection with SR 57 in Townsend.

[1] No section of SR 251 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.

[4] SR 251 was established in 1949 along an alignment from its current southern terminus north-northwest and then northwest of the city, to what is now the unincorporated community of Cox.

[2][3] In 1955, a short section from Darien to northwest of I-95 was paved.