It runs from Interstate 90 (I-90) to U.S. Route 281 (US 281), and is maintained by the South Dakota Department of Transportation (SDDOT).

After leaving Plankinton, the road curves back to the east and continues through open plains for about one mile (1.6 km) before reaching its eastern terminus at an intersection with US 281.

It connects the town, via SD 258, to the Aurora Plains Academy (a youth treatment facility and school).

[citation needed] SD 203 begins at an intersection with SD 258, immediately crossing a railroad track before heading north through flat plains to pass by the Plankinton baseball field and have an intersection with County Road 32 (CR 32, E 3rd Street), before passing by a derby racetrack and a cemetery.

[citation needed] The entire length of SD 203 is a paved, rural, two-lane state highway.