It runs from Interstate 49 (I-49) in Carthage northwest to the Kansas state line.

Some (about half) of those last 10 miles (16 km) to Carthage, from its junction with I-49 Business at Madison Ave. in Webb City, are routed in a northeasterly direction.

This results in going northeast on southbound Route 171 and vice versa along this stretch.

However, I-49 Business is going more or less in its designated direction, north, in a wrong-way concurrency at the same time.

Kansas did not change K-57's number to match until 2004, when it became K-171 after it was decided to shorten K-57 because it had numerous concurrencies along its routing.