The area was originally settled by members of the Church of Jesus Christ of Latter-day Saints.

The newly established county was named for American president James Madison.

Madison County was declared a national disaster area after the flood of June 5, 1976.

They then closed their practices and collaborated with the community to build Madison Memorial, a non-profit healthcare system.

The region served includes the following counties Jefferson, Madison, Fremont, Teton, Clark, and Lemhi.

Other elected officials include clerk, treasurer, sheriff, assessor, coroner, and prosecutor.

In that same period Republican presidential candidates polled more than 90 percent of the county's vote on three occasions, Ronald Reagan in 1984,[5] George W. Bush in 2004,[6] and Mitt Romney in 2012.

However this was still a lower vote share than those achieved by Republican candidates George W Bush in 2000 and 2004, John McCain in 2008 and Mitt Romney in 2012.

Biden's vote share was the highest for a Democrat in a presidential race in this county since 1996.

It was also one of just four times since Lyndon Johnson's 1964 landslide that a Democrat exceeded 15% (the others being the aforementioned 1996, as well as Jimmy Carter in 1976 and Hubert Humphrey in 1968).

At the state level Madison County is located in Legislative District 34,[12] which currently has an all-Republican delegation in the Idaho Legislature.

As of the 2010 United States Census, there were 37,536 people, 10,611 households, and 7,887 families living in the county.