South Dakota is a U.S. state in the Midwestern region of the United States. South Dakota is the seventeenth largest by area, but the 5th least populous, and the 5th least densely populated of the 50 United States. As the southern part of the former Dakota Territory, South Dakota became a state on November 2, 1889, simultaneously with North Dakota. South Dakota is bordered by the states of North Dakota, Minnesota, Iowa, Nebraska, Wyoming, and Montana.

Rhode Island, officially the State of Rhode Island is a state in the New England region of the United States. It is the smallest U.S. state by area and the seventh least populous (1,059,361 as of 2019), but it is also the second most densely populated behind New Jersey. The state has land borders with Connecticut to the west, Massachusetts to the north and east, and the Atlantic Ocean to the south via Rhode Island Sound and Block Island Sound. It also shares a small maritime border with New York.