Keep the loop to the Northern Hills for a true day trip. Mount Rushmore and the Southern Hills deserve more time than a rushed out-and-back.
Belle Fourche
Belle Fourche is the practical northern gateway. Pair it with Hulett and Aladdin for a scenic route that avoids simply retracing the interstate.
Spearfish and Spearfish Canyon
Spearfish offers meals, lodging and a lively downtown. The canyon adds waterfalls, limestone walls and a beautiful drive, but it deserves several hours of its own.
Deadwood and Lead
Choose these neighboring towns for Black Hills mining history, architecture and entertainment. They are a strong afternoon or overnight continuation after a morning Tower visit.
Sturgis
Sturgis is close to I-90 and a natural stop for motorcycle travelers. During the annual rally, traffic, lodging and drive times change across the entire region.
What about Mount Rushmore?
You can drive from Devils Tower to Mount Rushmore in one day, but the route becomes transportation rather than exploration. If Rushmore, Custer State Park or the Southern Hills matter to you, plan at least one Black Hills overnight.