The county is the state's economic and industrial center, having the resources of the Port of Portland, the Maine Mall, and having corporate headquarters of major companies such as onsemi, IDEXX Laboratories, Unum, and TD Bank.

North and west of Sebago Lake, the terrain of the county begins to flow into the foothills of the Appalachian Mountain range.

As of the 2010 United States Census, there were 281,674 people, 117,339 households, and 70,778 families living in the county.

[11] In terms of ancestry, 22.7% were English, 21.1% were Irish, 9.0% were German, 8.4% were Italian, 6.0% were Scottish, 5.5% were French Canadian, and 4.4% were American.

Cumberland County also has its own treasury department, emergency management agency and also has a district attorney office.

The county remained steadfastly and overwhelmingly Republican even in Franklin D. Roosevelt's huge Democratic landslide win in 1936.

Cumberland remained in the Democratic column in 1968, backing Hubert H. Humphrey, who had chosen Maine Senator Edmund Muskie as his running mate.

Carter would narrowly win the county in 1980, marking the first time Cumberland had diverged from the rest of Maine in a presidential election, as the state would be carried by Republican nominee Ronald Reagan.

Reagan would easily carry Cumberland in his 49-state landslide re-election in 1984; however, it was Maine's closest county, with Democrat Walter Mondale losing it by a relatively narrow 13.7%.

In 1988, George H. W. Bush would become the last Republican, as of 2020, to carry Cumberland County at the presidential level, winning it by less than seven points.

In 1992, Democrat Bill Clinton would win the county with nearly 43% of the vote against Bush and independent Ross Perot; it would be the last time a Democrat would receive less than 50% of the vote in Cumberland County in a presidential election.

King makes passing reference to other nearby towns and cities, including Portland, Falmouth, and Westbrook.

The video game Trauma Team takes place in Cumberland County in the year 2020, referencing Portland and its Back Cove neighborhood.

Neither actual hospital housed in Portland is mentioned in-game; instead, a fictional trauma center called Resurgam First Care is fabricated for the plot (in real life, Portland's city motto is "Resurgam", Latin for "I will rise again").