24.8% were of English, 14.7% United States or American, 12.7% Irish, 8.5% French and 5.6% German ancestry.

24.90% of all households were made up of individuals, and 9.60% had someone living alone who was 65 years of age or older.

As of the 2010 United States census, there were 38,786 people, 16,431 households, and 10,627 families living in the county.

[14] In terms of ancestry, 26.3% were English, 21.0% were Irish, 19.0% were French, 9.2% American, 7.0% Scottish, 6.6% Italian, 2.7% Polish, and 2.2% Scotch-Irish.

[17] Prior to the late 20th century, Waldo County was a solidly Republican county, going for the Democratic nominee only once between 1920 and 1988 — the one Democratic victory was Lyndon B. Johnson's landslide victory in 1964.

Waldo was one of a handful of counties nationwide that voted for independent Ross Perot in 1992.

In each election since 2004, Waldo County has been won by a Democrat, but never with more than 55% of the vote.

[1] Waldo County features in Nathaniel Hawthorne's classic novel The House of the Seven Gables as the site of extensive landholdings once claimed by the formerly aristocratic Pyncheon family.