Sac (or Sauk) Indians, a tribe of the Algonquian linguistic family, closely related to the Fox and Kickapoo tribes. Sac is a shortening of their Indian name, Osakiwug, which probably means “people of the yellow earth.” Originally the Sac lived near Saginaw Bay in Michigan. In the 17th century they settled near what is now Green Bay, Wisconsin. In the 18th century they united with the Fox Indians and moved southward, founding their chief village near what is now Rock Island, Illinois. Estimates of the Sac and Fox population in about 1800 range from 3,000 to 6,000.

The Sac and Fox aided Britain in the War of 1812. In the late 1820's the United States government ordered the Sac and Fox to move west of the Mississippi River in accordance with a treaty signed in 1804. Some of the Indians then settled in Iowa under the leadership of Keokuk. The rest, led by Black Hawk, fought for their Illinois lands in the Black Hawk War of 1832, but they were also forced to move to Iowa. In 1842 the Sac and Fox sold their Iowa lands and moved to Kansas. Some later returned to Iowa, and others moved to Indian Territory (Oklahoma). Today, most Sac and Fox live on or near tribal areas in Iowa, in Oklahoma, and on the Kansas-Nebraska border.