Franchisee Lou Groen invented this fried fish sandwich in 1962 to appeal to his customer base — a predominantly Roman Catholic community that abstained from eating meat on Fridays. The Filet-O-Fish's popularity showed that offering a non-hamburger item could be profitable and helped it eventually make its way into the national menu in 1965. 

To improve profits, Jim Delligatti, a franchise owner, created a two-patty burger, a bigger sandwich than what McDonald's had been offering at the time, and called it the Big Mac. The new addition was met with roaring success. By 1968, it was served in McDonald's restaurants all across America and is now one of the chain's signature products. The company may play around with different Big Mac sizes, but the iconic sandwich itself is here to stay.

Looking to offer a meatier burger, franchisee Al Bernardin created the Quarter Pounder in 1971. Customers responded well to the heftier quarter-of-a-pound beef patty and the burger made its nationwide debut in 1972.

Today, McDonald's is known for its all-day breakfast menu, but until the 1970s, the chain had only been a place for lunch and dinner. That changed when franchisee Herb Peterson invented the Egg McMuffin in 1971, paving the way for McDonald's foray into breakfast. Since its official addition to the menu in 1975, the breakfast sandwich has become a McDonald's classic.

Advertising executive Bob Bernstein conceived the idea for the Happy Meal for his key client, McDonald’s, when the chain recognized that their restaurants needed to better accommodate families with children. The kid-friendly meal rolled out nationally in 1979 and has since become a vital part of McDonald’s success.

The McRib was first introduced in 1981, but did poorly in sales — leading to its removal in 1985. However, the boneless pork patty sandwich developed a cult following over the years and the fast-food giant has learned how to capitalize on its demand through its scarcity. The McRib makes appearances back onto McDonald's menu as a limited-time offer — much to the delight of diehard fans.

Invented by McDonald's first executive chef, René Arend, these bite-sized fried chicken pieces were well-received by consumers following their nationwide addition in 1983 and helped McDonald's continue to expand their menu beyond hamburgers.

When McDonald's began offering salads, it marked the chain's attempts to reinvent its fast-food image and appeal to a more health-conscious consumer. 

The Chicken McGrill and Crispy Chicken sandwiches were added to the national menu — diversifying McDonald's sandwich offerings and broadening its range of chicken products.

In 2002, McDonald's launched its first national value menu, the Dollar Menu, which served customers a choice of eight products for just $1 each.

McDonald's continued to develop its popular breakfast menu with the introduction of the McGriddle — a breakfast sandwich made with bacon, egg, cheese and hot griddle cakes.

Seeking to grow the business and evolve the McDonald's experience, the chain made the McCafé program, a line of special drinks including lattes and mochas, available across all U.S. restaurants in 2009 — creating competition for other coffee-providing chains such as Starbucks and Tim Horton's.