Iowa Highway 3 (Iowa 3) is a state highway that runs from east to west across the state of Iowa. It is the longest state highway in Iowa, at 323 miles (520 km) long. Iowa 3 begins at the South Dakota state line where it continues as South Dakota Highway 50 and ends at the Northwest Arterial at the Dubuque city limits. It is designated the American Veterans Memorial Highway for its entirety. It is located approximately halfway between Interstate 80 and Interstate 90.

Iowa Highway 4 is a state highway which runs from north to south across the state of Iowa. It is 146 miles (235 km) long, beginning at an intersection with Iowa Highway 44 in Panora and ending at the Minnesota state line north of Estherville. It continues north as Minnesota State Highway 4. The route was created on January 1, 1969, when several route designations were changed to match other states' route numbers. Before 1969, Iowa 4 was known as Iowa 17.