Monday was not only Labor Day but also National Cheese Pizza Day, which prompted people to enjoy a slice to celebrate the holiday.

More than 2 billion pounds of pizza cheese is produced in the United States.

A 2014 study by U.S. Department of Agriculture says about 1 in 8 Americans consume pizza on any given day.

Unlike Labor Day, National Cheese Pizza Day is not a federally recognized holiday.

It's unclear who came up with the idea to also designate Labor Day as National Cheese Pizza Day.