Although fewer companies fly the skyward tow ads, those who do claim business is booming and data backs them up.

The Fourth of July Parade in Banner Elk, N.C., on Friday. Getty Images Residents gather to watch as the Independence Day parade passes by Storm Lake, Iowa, on Friday.

“One of our big objectives is to sell 100,000 shirts, which would equate to $1 million to a nonprofit, so that’s like a big, audacious goal of ours,” Daake said.

Report on the Star-spangled banner, Hail Columbia, America, Yankee Doodle by Sonneck, Oscar George Theodore, 1873-1928; Library of Congress. Music Division ...