CINCINNATI -- “Advertising,” mystic Thomas Merton wrote, “treats all products with the reverence and the seriousness due to sacraments.”

Well, then, I’ve been to advertising’s Vatican and worshiped at the altar like a zealot.

The American Sign Museum in Cincinnati traces Yankee commercialism from the country’s first hand-lettered brands and gilt-edged placards through the garish glare of neon-backed Jetsonian plastics.

It’s a 60-year sweep that took Americans from doe-eyed innocents spotting their first trade signs — a giant shoe, a huge hat — to Mad Men sophisticates who knew all about satellites and Saran Wrap.

It took a lot more to catch our eye with each succeeding decade, so the dainty painted signs of a century ago soon crumbled in the onslaught of the light bulb. Then that was not enough, and we ogled the marvel of neon gas.

Finally, in a moment right out of The Graduate — “Plastics!” — we could have it all: glowing, flashing, whirling enticements that filled the horizon to infinity.

The American Sign Museum has been fascinating since collector Tod Swormstedt opened it in 2005 in a scruffy artists’ co-op near downtown Cincinnati. But it always felt claustrophobic, as Swormstedt found more signs. He also picked up the phone every day to hear about a roadside relic that needed a new home — fast. If he didn’t take it, another little bit of Americana would deconstruct into landfill.

This summer, Swormstedt and his volunteers moved into a century-old factory in the working-class Camp Washington neighborhood just north of downtown Cincinnati, and have nearly four times the space. They’re busy filling the Machine Flats building to its 28-foot rafters with signs, posters, photos, catalogs, salesmen’s samples and signage tools that were previously in storage.

Now the artifacts can breathe within these old brick walls, and visitors can wander along a signage time line from early lettering through a Sputnik satellite inspiration for a California shopping center.

The museum’s centerpiece is blinking, flashing Main Street, whose storefronts were hand-painted by some of the best in the business. Sign artists from the United States and Canada descended upon the old factory this summer to paint rows of American shop fronts, from a 1910s jewelry shop to a ’40s TV and radio store and a Marshall Field, ready for the original 1950s department store signage from State Street, Chicago.

Each storefront was carefully matched to its sign, and in the middle of the commercial district, a giant McDonald’s sign lures the hungry and a tracer-light Holiday Inn sign beckons weary travelers.

For travelers of a certain age, much of the museum feels like a Griswoldesque family road trip. There’s Howard Johnson! Can we get an ice cream cone? There’s Big Boy! Can we get a hamburger? There’s Holiday Inn! Can we get a room and go swimming?

After highway beautification, our roads look less cluttered now, but the American Sign Museum lets us realize how much blinking, whirling, flashing and twirling excitement we’ve lost along the way.

There’s “Dolly Madison Ice Cream” in neon vying with a luminescent Colonel Sanders. Big Boy once tried to out-glow “McDonald’s 15¢.”