Few companies operate for more than a century, and many falter after they hit the century mark. Retailer Sears, Roebuck & Co. opened its first store in 1892, eventually becoming the largest store chain in the country. Today, it operates less than two dozen stores, which means it has basically disappeared.

On the other hand, some of America’s most famous companies, started in the early 20th Century – or earlier – have survived. Henry Ford started making automobiles in 1903. AT&T began operations in 1885. But the oldest company in the Fortune 500 got its start more than a century earlier – Bank of New York Mellon, which traces its origins to 1784.

Experts on corporate history sometimes debate why some companies succeed and others go out of business. Sears did not evolve into a big-box discount retailer as Walmart did, and with e-commerce becoming a critical part of the retail landscape, Sears did not try to compete with Amazon. Ford might have been destroyed as dozens of other car companies started over the first third of the 20th Century. GM eventually grew larger, but Ford stayed near the top in its industry. (These are America’s oldest car brands.)

According to a study by management consulting firm McKinsey, the average lifespan of a company on the S&P 500 list of publicly traded enterprises was 61 years in the late 1950s. In 2016, it had fallen to just 18 years. Today, companies are merged, bought out, or simply go belly up at a much faster pace than they used to.

The longevity of companies reported by another index, the Fortune 500 – which compiles the largest 500 U.S. publicly traded and private corporations based on revenue – is comparable, according to Mark Perry, senior fellow of the right-leaning American Enterprise Institute. Perry found that in 2019, only 52 companies have been on the Fortune 500 list since its inception in 1955.

Click here to see the oldest companies in the Fortune 500

Why only about one in 10 of these companies have lasted for at least 64 years is a matter for academic discussion. One popular explanation is the concept of creative destruction, which says that in order to innovate, we need to dismantle the old. Companies, therefore, cease to exist (at least in their original configurations) when they’re supplanted by companies involved in newer industries and innovations. (These are the 55 oldest continuously sold products in America.)

To determine the oldest company in the Fortune 500, 24/7 Wall St. reviewed data on Fortune’s website, ranking companies based on their founding date. Data on annual revenue and the number of employees also came from Fortune.