Underwood is a city in Pottawattamie County, Iowa, United States. The population was 688 at the 2000 census.
Underwood is located in Norwalk Township, so the early history of the township is also of the town. The historical information provided here was taken from a book on Pottawattamie County's past. The principal early settlers of the area arrived during the period from 1845 to 1850. In 1847, a flour mill and a saw mill were built on Mosquito Creek, southwest of the present site of Underwood. In 1850, the flour mill was destroyed by a flood. The first school was built in 1863 and soon more homes were built near the school and saw mill. It became known as Downsville. A post office was established there.
With the coming of the Chicago, Rock Island and Pacific Railroad in 1869, the town of Underwood was established three miles northeast of Downsville, which was later abandoned and has entirely disappeared (with the exception of a cemetery). In 1882, the other railroad that crossed through Norwalk Township, Chicago, Milwaukee and St. Paul, built a station house, erected a water tank and laid a switch. These improvements were on portions of the farms owned by two men and their farms were to be surveyed and divided into town lots. The name Underwood comes from the name of the first engineer to run a train over the Milwaukee tracks. Two farmers cut the corn stalks off to make a road to the Milwaukee tracks so the depot could be built. This path later became "Main Street".