[3] Grundy County is included in the Waterloo-Cedar Falls, IA Metropolitan Statistical Area.

It was named after Felix Grundy of Tennessee, a statesman, Senator, member of the House of Representatives and Attorney General under President James K. Polk.

The wooden, two-story building contained a courtroom, but was used for other purposes, including housing the office of the sheriff, county treasurer, the judge, as well as a chamber for the jury.

The population ranking of the following table is based on the 2020 census of Grundy County.

The first occasion was in 1912, when former Republican Theodore Roosevelt won the county as the Progressive candidate.

During his two landslide victories of 1932 and 1936, Franklin D. Roosevelt became the first Democrat to win Grundy County in its history.

The final time a non-Republican candidate carried the county was in 1964, when Lyndon B. Johnson won in a nationwide landslide.

No Democratic candidate has ever received more than 60% of the vote in the county, and in the last twenty-one elections (beginning in 1944), the Republican obtained at least 60% of the vote in sixteen of them, and the Republicans have hit at least 65% in ten of the twenty-one elections in that span.