The mainland, which is part of the Everglades, comprises 87% of the county's land area and is virtually uninhabited with only 17 people recorded in the 2020 census.

More than 99.9 percent of the Monroe County population lives in the island chain known as the Florida Keys.

Two thirds of the large area in what local residents call "mainland Monroe" is uninhabited by virtue of being part of the Everglades National Park, and the remainder by the Big Cypress National Preserve in the northeastern interior.

The area, officially named Cape Sable Census County Division, is virtually uninhabited.

[7] In mainland Monroe, the only three populated places appearing on detailed maps and in the USGS geographic name database are Flamingo, Pinecrest, (not to be confused with much larger Pinecrest of neighboring Miami-Dade County), and Trail City.

Loop Road can be found on most maps as CR 94, although the roadway no longer has a numbered designation and is now managed by the National Park Service.

[8][9] The μSA is part of the Miami-Port Saint Lucie-Fort Lauderdale Combined Statistical Area.

As of the 2020 United States census, there were 82,874 people, 32,839 households, and 18,586 families residing in the county.

In 2005 Monroe County’s population was 75.1% non-Hispanic white, 17.7% Hispanic or Latino, 5.4% African-American and 1.1% Asian.

The Monroe County Sherriff's Office is responsible for law enforcement within the City of Marathon.

The Monroe County Sherriff's Office is responsible for law enforcement within the Village of Islamorada.

The Monroe County Sherriff's Office is responsible for law enforcement within the community of Key Largo.

A non-profit local arts agency, it makes grants, operates the Monroe County Art in Public Places program, sponsors seminars, and manages the on-line cultural calendar for the region.

From its inception through fiscal year end 2006, FKCA has awarded $433,916 in privately raised funds and grants to literary, visual and performing artists and cultural organizations.

The annual economic impact of the non-profit cultural community in the Keys is estimated at over $22 million.

However, unlike most Southern Democrats, Monroe County voters tended to be far more liberal on social issues such as civil rights and later gay rights, voting decisively for Lyndon B. Johnson in 1964 and even supporting Hubert Humphrey in 1968, one of only three Florida counties to do so.

Four years later, however, Richard Nixon easily carried the county in his 1972 landslide re-election, becoming the first Republican winner since 1888 by receiving over 70% of the vote.

Although Monroe voted for the Democratic candidate from 1992 to 2012, it was won by consistently narrow margins, such as 0.5% in 2004 and 2012.

Barack Obama in 2008 was the first candidate for president to win a majority, 51.7%, of the vote since George H. W. Bush's national landslide victory in 1988.

Monroe County is home to a large LGBT community, particularly in Key West.

The library provides access to PCs with internet and word processing capabilities.