Federally recognized tribes
Today the federally recognized Sac and Fox tribes are:

Sac and Fox Nation (Meskwaki: Othâkîwaki, meaning: "People of the yellow earth"), headquartered in Stroud, Oklahoma;
Sac and Fox Tribe of the Mississippi in Iowa (Meskwaki: Meshkwahkîhaki, meaning: "People of the red earth"), headquartered in Tama, Iowa; and
Sac and Fox Nation of Missouri in Kansas and Nebraska (Meskwaki: Nîmahâhaki), headquartered in Reserve, Kansas. Language
Sauk is a dialect of the Fox language, one of the many Algonquian languages. It is very closely related to the dialects spoken by the Meskwaki and the Kickapoo tribes. Each of the dialects contains archaisms and innovations that distinguish them from each other. Sauk and Meskwaki appear to be the most closely related of the three, reflecting the peoples long relationship. Sauk is considered to be mutually intelligible, to a point, with Fox. In their own language, the Sauk at one time called themselves asakiwaki [a-sak-i-wa-ki], "people of the outlet". The Sauk people have a syllabic orthography for their language. They published a Primer Book in 1975, based on a "traditional" syllabary that existed in 1906. It is intended to help modern-day Sauk to learn to write and speak their ancestral tongue. A newer orthography was proposed around 1994 to aid in language revival.
They had been banished from their tribe for murder. According to Anishinaabe oral tradition, these five Sac were killed by local Dakota in the late 18th century.Place names with "Sauk" references include: 

Iowa: Sac City, Sac County, and Sac Township. Illinois: Sauk Village; Sauk Valley: the cities of Dixon, Sterling, Rock Falls and the surrounding area; Sauk Trail, a winding road south of Chicago, said to follow an old Indian trail; Johnson-Sauk Trail State Recreation Area; and Black Hawk College [Moline and Kewanee, IL]. Michigan: The name of Saginaw is believed to mean "where the Sauk were" in Ojibwe; and the Saginaw Trail is said to follow an ancient Native American trail. US Route 12 in Michigan is said to follow the Sauk Native American trail. Minnesota: City of Sauk Centre, Le Sauk and Little Sauk townships, Lake Osakis, Sauk River, Sauk Rapids.