[3] Naturalist John Muir and his parents first settled in the US in 1849 on a farm in Marquette County.

The highest altitude in the county is a rocky area known as Mt.

As of the census[11] of 2000, there were 15,832 people, 5,986 households, and 4,166 families residing in the county.

45.7% were of German, 8.2% Irish, 6.9% Polish, 6.1% English, 5.6% Norwegian and 5.1% American ancestry.

25.40% of all households were made up of individuals, and 12.30% had someone living alone who was 65 years of age or older.

In 2020, Donald Trump received the highest share of the vote for any candidate in the county since 1960 and won by an even bigger margin in 2024.