[3] The county was founded in 1865;[4] at the time it was part of the Montana Territory.

[5] In presidential elections, Madison County has historically voted predominantly Republican, with Franklin D. Roosevelt the only Democrat to carry the vote since 1916, the last of the three times he did so being in 1940.

[citation needed] As of the 2010 census, there were 7,691 people, 3,560 households, and 2,192 families residing in the county.

The racial makeup of the county was 96.8% white, 0.5% American Indian, 0.3% Asian, 0.2% black or African American, 0.8% from other races, and 1.4% from two or more races.

In terms of ancestry, 31.0% were German, 19.7% were English, 18.9% were Irish, 7.3% were Norwegian, 5.9% were Swedish, 5.0% were Scottish, and 2.9% were American.