In 1919, Roy Allen, an entrepreneur out of California, bought a formula for root beer from a pharmacist in Arizona. He then made his own batch and started a root beer stand in Lodi, Calif. Three years later, he took on a partner, Frank Wright. Allen (A) and Wright (W) created A&W Root Beer and began expanding through franchising. The brand is still around, proving the model’s staying power.

World War II ended in 1945. That brought hundreds of thousands of young men back home, all of them looking for work and armed with separation pay and other financing to open franchises. The country also had pent-up demand from consumers who’d spent years conserving resources. The factors helped usher in a franchising boom in the 1950s.

In 1946, President Harry Truman signed the Lanham Act, establishing federal trademark law and enabling companies to sue people who use those trademarks without permission. Because franchises are brands that are generally based around a single set of trademarks, that law would protect franchises selling the right to use a brand name.

Another early adopter of franchising was Harland Sanders, better known as Colonel Sanders, the legendary founder of what is now KFC. Sanders had started his business selling chicken out of his service station in 1930. The first Kentucky Fried Chicken franchise opened in Utah in 1952.

In 1954, a milkshake machine salesman named Ray Kroc visited a restaurant run by Richard and Maurice McDonald, wondering why they used so many of his machines. Kroc ultimately convinced the brothers to let him sell the rights to franchise the business across the country. McDonald’s would ultimately become the largest, most successful restaurant business on the planet.

Dwight D. Eisenhower signed the Federal-Aid Highway Act in 1956. That’s the piece of federal legislation that would lead to the construction of the country’s interstate highway system, arguably the biggest public works project in history. The Interstate system would change the U.S., and the restaurant industry, providing the country with hundreds of exit ramps where restaurant franchises like A&W, KFC and McDonald’s built their locations.

In 1960, a group of entrepreneurs gathered in Chicago to talk about the future of franchising as unscrupulous franchisors gave the business a bad name during its rapid growth period of the 1950s. One of the entrepreneurs, Dunkin’ Donuts founder Bill Rosenberg, slapped $100 on the table and said, “What we need is an association!” The International Franchise Association was born.

Growing concern about the aforementioned unscrupulous franchise sellers ultimately got regulators involved. In 1970, California became one of the first franchisors to require franchisors to register with the state before they could sell franchises to investors. The U.S. Federal Trade Commission would follow with its own disclosure rule in 1978.

In November 1987, KFC opened a location in Beijing, China as part of a joint venture by companies there. It was the first western brand in China, setting the stage for rapid growth of franchises in the country. It marked a new period of international growth for U.S.-based franchises, signaling that most countries, even those with significant political differences with the West, are potential markets.

Private-equity groups began investing heavily in franchisees in the 1990s. At the same time, more franchises, like Yum! Brands and IHOP, began selling large swaths of stores to operators. The result? Giant operators like Flynn Restaurant Group and NPC International now operate coast-to-coast organizations with well over $1 billion in annual revenue.

In 2014, the National Labor Relations Board’s general counsel, Richard Griffin, asserted that McDonald’s could be liable for the labor practices of its franchisees. The NLRB’s “joint employer” effort since then, while not yet decided, could be a watershed moment in franchising, potentially forcing franchisors to exert more control over their operators’ employment decisions. It could also give labor unions inroads into the restaurant industry — something they’ve pushed recently with an effort to increase wages at quick-service restaurants to $15 an hour.