CNN  —  If you’re wondering how much your car is worth, or how much to pay for that car you’re thinking of buying, there’s a good chance you’ll check KBB.com. That’s short for Kelley Blue Book, and it’s one of the longest-standing sources for used car values there is. A man who was instrumental in its rise to prominence, Bob Kelley, died on May 28 in Indian Wells, California, at the age of 96. The Blue Book’s origins lie in the Kelley Kar Company of Los Angeles, a used car daelership founded by Bob’s uncle, Les Kelley, in 1918 with a few Model T Fords. Wanting to grow his inventory, Kelley Kar Company circulated a list of cars it wanted to buy and how much it would pay for them. By 1926, that list turned into the first Kelley Blue Book pricing guide for used cars. The Kelley Blue Book logo as it appeared on a 1926 pricing guide. Cox Automotive/Kelley Blue Book Long ago, Bob Kelley was a “lot boy” at the dealership run by his uncle and his father, Sidney “Buster” Kelley. He did things like filling tires. Eventually, he took charge of fixing up used cars and estimating their resale value, the kind of figures that would go into the paper guide. By the 1960s, that book became the whole business. The family sold the car dealership and sold the pricing guide, separately, to a private investor, said Bob Kelley’s son-in-law Charlie Vogelheim. Buster and Bob Kelley both signed 40-year management contracts to continue running operations, though, he said. The entrance to the Michigan Central Station is seen, Monday, May 13, 2024 in Detroit. A once hulking scavenger-ravaged monolith that symbolized Detroit's decline reopens this week after a massive six-year multimillion dollar renovation by Ford Motor Co., which restored the Michigan Central Station to its past grandeur with a focus squarely on the future of mobility. Carlos Osorio/AP Related article An icon of Detroit’s ruin is now a symbol of Motor City’s economic resurgence For most of the first 30 years as a stand-alone business, the Blue Book was largely an industry source, not something for the general public to use, according to KBB.com. Car dealers, finance companies and insurance companies relied on its values and the book helped shape how people thought about what cars are worth. Kelley Blue Book claims to be the first to show the effect of mileage on a used vehicle’s value, for example. Other related products were added over the years, including a new car pricing guide in 1966, RV and motorcycle guides and even a “Manufactured Housing” price guide. In 1995, Kelley Blue Book started a website, making its data easily accessible to the general public, not just industry insiders. Still, the book continued in publication every two months for several more years, said Vogelheim, because not everyone was using the Internet. “The nice thing about the new technology is you could get fresh values distributed more frequently and more specific in terms of your information,” he said, “but, you know, the book, if you dropped it, it’d still work. You didn’t have to plug it in and recharge or anything like that.” Bob retired from the company in 2000. Vogelheim worked with him at Kelley Blue Book starting in 1985 and was there when Kelley retired. An electric car charges at a station in Oakland, California in 2020. Santiago Mejia/The San Francisco Chronicle/Getty Images/File Related article While new electric vehicle sales are slowing, used sales are ramping up “Bob was my mentor, going through all of the vehicle values, relationships between the different vehicles and, of course, the whole operation of publishing the book,” Vogelheim said. “Before the computer, we did it internally, the whole set up and delivery of the proof sheets and then the actual printing and distribution.” The last step in the production process was rounding off the corners of the small book so dealers could easily slip it into a shirt pocket, he said. Bob Kelley also taught people to pay attention to what customers actually valued and would pay for in their cars, which was more complicated than just subtracting a certain amount from the price of the new car. For instance, some early 1990s Lexus cars came with a phone installed as an expensive option, said Vogelheim, but, when the cars were sold as used, the clunky corded phone actually reduced the car’s value. “It was in the way,” he said. Kelley Blue Book and its website, KBB.com, were purchased by the auto sales website Autotrader in 2010, becoming part of the privately owned conglomerate Cox Enterprises. There were, and are, competitors to Kelley Blue Book, of course. A company called Edmunds started its own consumer-focused pricing guide in 1966, and it also went online in 1995 as another source of automotive pricing information. But Kelley Blue Book was one of the very earliest to create a standard way for shoppers and the industry to gauge the value of a used car.