Photo: Sarahbeth Maney / Special To The Chronicle Photo: Sarahbeth Maney / Special To The Chronicle Photo: Sarahbeth Maney / Special To The Chronicle Photo: Courtesy A&W Restaurants Photo: Courtesy A&W Restaurants Photo: Sarahbeth Maney / Special To The Chronicle Photo: Sarahbeth Maney / Special To The Chronicle

For more stories like this, check out The Chronicle's weekly Travel newsletter! Sign up here.

Pete Knight was working on the schedule in the office of the St. Helena A&W when an employee came looking for him. A woman was waiting up front holding a brown paper sack, and she wanted to speak to the manager.

“I want to give these back,” she said, handing him the bag.

Inside he found six or seven vintage glass A&W mugs from the ’50s and ’60s. She had stolen the mugs when she was a teenager, and held on to them for decades.

“I’m a born-again Christian, and I want it off my mind,” she explained.

Knight accepted the mugs and put them on display in the restaurant on a whim. As soon as he did, customers noticed. They started pointing out ones in their own collections, recounting memories of A&W from childhood road trips and days of root beer floats gone by. Inspired, Knight started actively building a collection, scouring eBay and even taking trips to other states to secure rarities. As time went by and the collection grew, people would bring in items to donate.

He now estimates his collection includes upward of 3,000 pieces of A&W memorabilia, including some of the earliest known canisters of the brand’s root beer syrup, old black and whites from historic A&W drive-ins, and seemingly every era of mug.

Knight got his first job at 16 years old at the San Rafael A&W, in the recognizable pilgrim hat building along Highway 101, after hearing that a couple of friends were planning to quit.

“I went down and I applied, and the guy handed me an apron and said, ‘Here you go,’ and started me in the kitchen. I didn’t even go home. I called my mom and said, ‘I’m working,’” Knight recalled.

He’s been with A&W ever since, working his way from the kitchen to management to franchisee. Today, Knight owns two A&W franchises, one in St. Helena and the other in Lodi, where the iconic American brand was born 100 years ago this June.

In 1919, Roy Allen, who had purchased a recipe for root beer from an Arizona pharmacist, opened his first location on Pine Street in Lodi. The timing couldn’t have been better. He put up a temporary stand just in time for a parade celebrating soldiers returning from World War I, serving up ice-cold root beer in frosty glass mugs for 5 cents on a hot June day.

By January, Prohibition was the law of the land: good news for an entrepreneur selling a soft drink with “beer” in the name. Members of the temperance movement had briefly tried to ban root beer in 1895, assuming that it must be alcoholic; now they had accidentally given it a big boost. The soda industry prospered during Prohibition, and many breweries switched to making soft drinks to stay afloat.

Allen partnered with one of his Lodi employees named Frank Wright and the pair expanded to Sacramento, opening California’s first drive-in restaurant at 16th and K streets. Allen bought out Wright after a short time, but the name stuck: A&W.

Photo: Courtesy A&W Restaurants

In the world of fast food, Allen was an early mover. White Castle officially launched in Wichita, Kan., in 1921; the first McDonald’s wouldn’t open its doors in San Bernardino until 1940. For the early years of A&W, however, Allen stuck with root beer and snacks.

“We didn’t sell french fries and hamburgers back in those days — it was popcorn and peanuts. If you got a sandwich, it was on sliced bread,” said Knight.

In the mid-1920s, Allen struck upon a faster way to grow: franchising. Unlike today, many of the early A&Ws were essentially pop-ups: simple stands that were open just during the summers along California’s Central Valley highways, selling root beer and snacks to travelers. To attract franchisees, A&W advertised that you could earn a year’s income in just six months.

One early franchisee was J. Willard Marriott. He had passed through Washington, D.C., on one of its typical steamy summer days and had a flash of inspiration: This was a town in dire need of cold refreshment. In 1927, he and his wife, Alice, bought the franchise rights for the first A&W in the nation’s capital. The following year, the Marriotts expanded with two more of their “Hot Shoppes,” including the first drive-in on the East Coast. It wasn’t until 1957 that the Marriott family moved into the business they’re known for today: hotels.

Over 100 years, A&W has seen its share of ups and downs, weathering the Great Depression and a labor shortage during World War II, and surging after the war thanks to the postwar embrace of fast food and drive-in culture.

After Allen sold the business and retired in 1950, A&W changed ownership multiple times, spun off an independent Canadian chain, expanded to Asia, and launched a bottled beverage business (with at least one ad starring Mr. T). Today, A&W has nearly 1,000 restaurants in the U.S. and Asia, owned by a partnership of franchisees, who are steering the brand back to its roots and growing the chain once more.

Photo: Car Culture Collection / Getty Images Plus

Many of us have fond childhood memories of fast-food chains; they evoke a certain ketchup-encrusted nostalgia in the hearts of Americans. But A&W’s history — and, let’s be honest, the root beer floats — have created a uniquely devoted fan base. In honor of the 100th anniversary, a pair of fans took a cross-country road trip to Lodi, stopping in A&Ws along the way (including one in Lodi, Wisconsin), and documented their journey on the A&W Fan Club group on Facebook. People call up Knight throughout the year looking to buy mugs for weddings and baby showers, which he is happy to provide.

Another fan: Huell Howser, host of “California’s Gold” and never one to turn down ice cream. Howser came by Knight’s Lodi restaurant to shoot an episode and was surprised to find that there was no plaque to commemorate the spot of Roy Allen’s first A&W. In fact, there was a plaque: it was sitting in Pete Knight’s office waiting for the city of Lodi to let him install it.

The episode of “California’s Gold” aired, and suddenly the city wanted to make it happen.

“I love history, and I love root beer,” announced Howser one year later at the official unveiling of the plaque. “Now we can celebrate what happened here historically.”

There are other places to celebrate A&W history around the state, but the number has dwindled. Many of the classic A&W drive-ins around California have closed or transformed into other businesses over time (the South Lake Tahoe location is now a branch of Chicken in a Barrel), but Modesto, Visalia and Hanford still have vintage A&W drive-ins with carhop service. In Modesto, the carhops still use roller skates in a nod to the city’s “American Graffiti” ties.

This may also account for A&W’s enduring charm: Each one is different. The older locations can be particularly quirky. Menus across the country are tailored to hometown audiences: pork tenderloin sandwiches in the Midwest, burritos in the Southwest, veggie burgers in California. The Lodi restaurant is one of a handful serving Beyond Meat plant-based burgers. But there’s one thing you can always count on at an A&W: root beer, made fresh daily and served ice cold.

“We serve our root beer in frosty glass mugs like Roy Allen did in 1919. He was very passionate about it, and we still are,” said Knight.

You can buy the mugs, including special 100th anniversary editions, but the mugs used in the restaurants still get stolen. Knight prefers to say people “borrow” them. Just like the people bringing their kids and grandkids back to a place they loved when they were young, sometimes the mugs come back too.

Photo: Courtesy A&W Restaurants

Dig Into A&W History

Memorabilia

Pete Knight’s collection of more than 3,000 pieces of memorabilia is on display inside his Lodi restaurant at 216 E. Lodi Ave. The plaque commemorating the birthplace of A&W is a few blocks away at 13 W. Pine St.

Drive-Ins

A few historic A&W drive-ins remain in California, including in Modesto (1404 G St.), Visalia (301 N. Willis St.) and Hanford (1113 N. 10th Ave.), where carhops still bring the food to your car — on roller skates if you’re in Modesto.

100th Anniversary

Celebrate the 100th anniversary of A&W Root Beer on June 21 in Lodi, with live music, giveaways and the unveiling of a new installation of a group of larger-than-life pieces of A&W history. A&W Restaurant, 216 E. Lodi Ave.

Cruise Nights

Classic cars and motorcycles show up every Thursday evening from April through October at the Lodi A&W. Hot rods, Elvis and karaoke come to the Modesto drive-in on Friday nights through the summer. In Visalia, cruise nights happen on the third Saturday of the month during the summer.

Andy Murdock is a freelance writer in Alameda. Email: travel@sfchronicle.com