Lou's Cafe was a diner in Hill Valley, located at Hill Street and Main Street. The cafe's owner was Lou Caruthers. In 1955 the hamburgers were 25¢, ham and cheese sandwiches were 30¢, and a chocolate sundae was 15¢. The cafe also served hot and cold drinks like coffee, milk (including flavors like chocolate), and Pepsi. The cafe had a Wurlitzer 1015 jukebox, filled with popular songs such as "The Ballad of Davey Crockett" and "Dance With Me Henry". It also had a payphone booth, with local calls costing 5¢.
Long before Lou founded the cafe, the site was originally the location of a bar known as the Palace Saloon during the 1880s. Sometime between 1885 and the early 1930s, the saloon was torn down and replaced with the Sisters of Mercy Soup Kitchen during the Prohibition era, which was active in 1931. Between 1931 and 1955, Lou came along and established the cafe, which became a popular spot for the young people of Hill Valley to hang out, particularly after school. By the 1980's, Lou's Cafe been replaced by fast food restaurants like Burger King as the popular place for young people to hang out. By 1985 it had been converted into Lou's Aerobic Fitness Center to capitalize in the aerobics trend of the era.
Marty McFly wandered in on November 5, 1955. He showed signs of being unaccustomed to the times by ordering a Tab, which Lou thought meant the bill, and told Marty he had to order something first. Marty then asked for a Pepsi Free, leading Lou to believe he wanted a Pepsi for free, as the drink Pepsi Free was not established yet, before finally settling on "something without any sugar" – a cup of black coffee. He also raised some suspicion from Lou when his digital watch alarm went off while he was trying to call Doc Brown on the cafe's payphone (as the digital watch had not yet been invented).
While at the cafe, Marty saw his father, George McFly, as a teenager. He also saw Biff Tannen and his cronies. There was also a possible disruption of the original space-time continuum when Marty tipped off Goldie Wilson that one day he would be mayor.
Another major event that occurred at Lou's Diner was George McFly asking Lorraine Baines-McFly to the Enchantment Under the Sea Dance and the ensuing altercation between Marty and Biff which led to a skateboard chase around the town square and ultimately ended in Biff's first manure encounter. Marty sat at Lou's Cafe at the end of his time in 1955 to write a warning letter to Dr. Emmett Brown about the night he went back in time (October 26, 1985).