It heads northeast and then due north; it ends at Iowa 3 near Remsen.

It goes northeast through Moville towards Kingsley adjacent to the Little Sioux River.

At Kingsley, Iowa 140 turns north and continues north for 16 miles (26 km) until it intersects Iowa Highway 3 southeast of Remsen, where it ends.

In 1931, Iowa 140 was extended south to Hornick and west to US 75 at Sloan.

It was extended west again in 1958 when I-29 was built, making its length 53 miles (85 km).