Though the line did not actually divide North and South, it became the symbolic division between free states and slave states. Today, it still stands for the boundary between northern and southern states.
An Americanism dating back to 1770–80
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The change was particularly pronounced in a swath from about the Mason-Dixon line to just north of Detroit, Chicago, and Nebraska.
From Washington Times ● Dec. 17, 2021
Several of the year’s most ambitious museums were in cities below the Mason-Dixon line.
From New York Times ● Dec. 7, 2021
But both rulings were widely ignored below the Mason-Dixon line, prompting civil rights activists to draw attention to the states' continuing segregation.
From Salon ● Apr. 24, 2021
The San Francisco Gay Men’s Chorus steps over the Mason-Dixon line for a multistate concert tour in the 2019 documentary “Gay Chorus Deep South.”
From Los Angeles Times ● Dec. 18, 2020
On the map, the division line between slave and non-slave societies occurs in Virginia, broadly anticipating the Mason-Dixon line that later split slave states from free.
From "1491" by Charles C. Mann
My parents insisted I apply to colleges below the Mason-Dixon Line and on the east side of Texas.
From The Wall Street Journal ● Jan. 20, 2026
That prompted the Maryland Legislature to pass a public accommodations law in 1963 banning discrimination in hotels and restaurants, becoming the first state below the Mason-Dixon Line to do so.
From Seattle Times ● Jun. 7, 2023
They are consumed with gusto and discrimination at nearly every party you might attend south of the Mason-Dixon Line, and although oblong and a bit thicker, they're sort of the grown-up version of a Cheez-It.
From Salon ● Jan. 22, 2023
“At the time, it was one of the very few institutions below the Mason-Dixon Line where African Americans could receive something higher than a high school diploma,” the National Park Service says on its website.
From Washington Post ● Mar. 1, 2022
But mainly it’s the way they’re so damned self-important, like they’d single-handedly stopped the dead at the Mason-Dixon Line or some nonsense.
From "Dread Nation" by Justina Ireland
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
