Marshalltown is a city in Marshall County, Iowa, United States and is the county seat of the county. With a population of 27,591 at the 2020 census, it is the 16th largest city in the state. Marshalltown is home to the Iowa Veterans Home and Marshalltown Community College.

Henry Anson was the first European settler in what is now called Marshalltown. In April 1851, Anson found what he described as “the prettiest place in Iowa.” On a high point between the Iowa River and Linn Creek, Anson built a log cabin. A plaque at 112 West Main Street marks the site of the cabin. In 1853 Anson named the town Marshall, after Marshall, Michigan, a former residence of his.

The town became Marshalltown in 1862 because another Marshall already existed in Henry County (In 1880, Marshall's name changed to Wayland). With the help of Potawatomi chief Johnny Green, Anson persuaded early settlers to stay in the area. In the mid-1850s, Anson donated land for a county courthouse. Residents donated money for the building's construction.

In 1863 the title of county seat transferred from the village of Marietta to Marshalltown. This event was the result of a considerable amount of political wrangling bordering on warfare. The determining factor was the location of the east/west railroad across Iowa and the winning company was the Cedar Rapids & Missouri River railroad under lease by the pioneer parent of the Chicago Northwestern Railway.

The young town then began growing. By 1900, Marshalltown had 10,000 residents. Many industries began developing in Marshalltown, like Fisher Controls, Lennox International and Marshalltown Company.

Marshalltown plays a small but significant role in the life of Ebe Dolliver, a main character in MacKinlay Kantor's Pulitzer Prize-winning novel "Andersonville" (1955).

Adrian Constantine "Cap" Anson, son of Henry and Jennette Anson, was the first European child born in the new pioneer town and is today known as Marshalltown's “first son.” Adrian became a Major League Baseball player and was inducted into the National Baseball Hall of Fame in 1939. He was regarded as one of the greatest players of his era and one of the first superstars of the game.

Baseball steadily became popular as Marshalltown grew in the mid-1800s. Adrian's brother Sturgis also became a talented baseball player and both went to play on intra-school teams at the University of Notre Dame. Both later returned to Marshalltown to play baseball for the town team. Along with their father Henry, the town's founder, they put together a team and became the most prominent team in the state of Iowa. The Marshalltown team, with Henry Anson at third base, Adrian's brother Sturgis in center field, and Adrian at second base, won the Iowa state championship in 1868. In 1870 Marshalltown played an exhibition game with the talented Rockford Forest Citys. Although Marshalltown lost the game, Rockford's management offered contracts to all three of the Ansons. Adrian accepted the contract, which began his professional career in baseball in 1871.