Yankton is a city in and the county seat of Yankton County, South Dakota, United States. Yankton had a population of 14,454 at the 2010 census and it is the principal city of the Yankton Micropolitan Statistical Area, which includes the entirety of Yankton County and which had an estimated population of 22,662 as of July 1, 2017. Yankton was the first capital of Dakota Territory. It is named for the Yankton tribe of Western Dakota people; Yankton is derived from the Dakota word I-hank-ton-wan ("the end village").Yankton is located on the Missouri River just downstream of the Gavins Point Dam and Lewis and Clark Lake, and just upstream of the confluence with the James River. The United States National Park Service's headquarters for the Missouri National Recreational River are located in the city. The Human Services Center was established as a psychiatric hospital in 1882 and is on the National Register of Historic Places. Yankton is commonly referred to as the "River City", due to its proximity to the Missouri River and the importance the river played in the city's settlement and development. Yankton has also earned the nickname "Mother City of the Dakotas", due to the early important role it played in the creation and development of the Dakota Territory, which later became the 39th and 40th U.S. states of North and South Dakota.Owing to the early exploitation of Fort Hays Limestone for cement manufacture, including shipment of cement to the construction of the Panama Canal, Yankton once also had the nickname "Cement City".

Sioux City () is a city in Woodbury and Plymouth counties in the northwestern part of the U.S. state of Iowa. The population was 85,791 in the 2020 census, which makes it the fourth-largest city in Iowa. The bulk of the city is in Woodbury County, of which it is the county seat, though a small portion is in Plymouth County. Sioux City is located at the navigational head of the Missouri River. The city is home to several cultural points of interest including the Sioux City Public Museum, Sioux City Art Center and Sergeant Floyd Monument, which is a National Historic Landmark. The city is also home to Chris Larsen Park, commonly referred to as "the Riverfront", which includes the Anderson Dance Pavilion, Sergeant Floyd Riverboat Museum and Lewis and Clark Interpretive Center. Sioux City is the primary city of the five-county Sioux City, IA–NE–SD Metropolitan Statistical Area (MSA), with a population of 168,825 in 2010 and a slight increase to an estimated 169,405 in 2018. The Sioux City–Vermillion, IA–NE–SD Combined Statistical Area had a population of 182,675 as of 2010 but had decreased to an estimated population of 178,448 as of 2018.Sioux City is at the navigational head, or the furthest upstream point to which general cargo ships can travel, of the Missouri River, approximately 95 miles (153 km) north of the Omaha–Council Bluffs metropolitan area. Sioux City and the surrounding areas of northwestern Iowa, northeastern Nebraska and southeastern South Dakota are sometimes referred to as Siouxland, especially by local media and residents. It is also a part of the Sioux Falls-Sioux City Designated Market Area (DMA), a larger media market region that covers parts of four states and has a population of 1,043,450.

South Sioux City is a city in Dakota County, Nebraska, United States. It is located immediately across the Missouri River from Sioux City, Iowa, and is part of the Sioux City, IA-NE-SD Metropolitan Statistical Area. As of the 2010 census, the city population was 13,353, making it the 14th largest city in Nebraska.

Le Mars is the county seat of Plymouth County, Iowa, United States. It is located on the Floyd River northeast of Sioux City. The population was 10,571 at the time of the 2020 census. Le Mars is part of the Sioux City metropolitan area.