State Highway 51 serves as a north–south route between Saint Paul, Falcon Heights, Roseville, and Arden Hills in Ramsey County.

It is not to be confused with nearby Ramsey County Road 51 (Lexington Avenue / Parkway), which runs parallel to State Highway 51 for much of its route.

After crossing over two railroad lines and entering Falcon Heights, the route passes along the east side of the Minnesota State Fairgrounds, making it a busy thoroughfare during the State Fair season.

The original alignment on the south end of Highway 51 was from West 7th Street up Edgecumbe Road to Snelling Avenue.

The northern terminus of the route was at old U.S. Highway 10, which is the present day junction of Snelling Avenue and County Road E in Arden Hills.

There was a plan until the 1970s to extend Highway 51 beyond its current northern terminus at I-694 in Arden Hills to proceed north to I-35W near Lexington Avenue in Blaine.