1955B was an ABC timeline and a year in the 20th century. The altered timeline it belonged to was created when an elderly Biff Tannen traveled from 2015 to give his younger self from 1955 a sports almanac to make himself rich.
- Gertrude Tannen is murdered by Uncle Lou, and Uncle Lou is murdered by Biff.
- Biff Tannen becomes rich after he takes the briefcase full of money from Uncle Lou, while he waits for 1958 to bet legally with the sports almanac once he turns 21.
- The Tannen residence was the home that Biff lived in with his grandma Gertrude.
Alternate timeline of events
For years in this timeline after 1955, see the Hell Valley timeline.
- Saturday, November 12:
- The elderly Biff Tannen arrived from 2015 to give his younger self a sports almanac. He explains how it works and tells his younger self that "a kid or a crazy, wild-eyed old man who claims to be a scientist" will be looking for the almanac one day. He then spent several hours reminiscing in the past before heading back to 2015.
- Terry tells Biff that he owes him $300 for fixing his car and getting rid of the manure (which happened four days earlier, from a skateboard chase with Marty McFly that caused him to crash into a manure truck).
- Biff gets intoxicated at the Enchantment Under the Sea dance, and tries to take advantage of Lorraine Baines. George McFly protects Lorraine, knocking Biff out with one punch.
- Sunday, November 13:
- Gertrude Tannen orders Biff to take her to Las Vegas so she can play the slot machines. She complains about the stench of the manure in the car, as well as on himself, and told him to come up with a better lie when he says he got the bruise on his face from falling down the stairs.
- Biff repeatedly tried to get his grandmother to bet for him at the Turf Club since the legal age to gamble was 21, and at 18, he was underage. He gave a $20 bill that he stole from a table to his grandmother to bet on the Chicago Bears. She didn't bet on the Bears, and they lost against the Los Angeles Rams, making Biff twenty dollars poorer. Biff told her to make another bet, on the Washington Redskins. However, when they beat the San Francisco 49ers, she only gave Biff back his twenty dollars, and kept the rest for herself. When Gertrude claimed Biff was as greedy as his father, Biff stated that he learned that from her.
- A shady man named Uncle Lou noticed the altercation, and noticed that Biff used a book to select the winners. He wanted to get a look at Biff's methods himself. He told Biff that they could earn money together, as he would be able to make the bets while Biff could not. Biff reluctantly agreed when Lou told him to wait for him in the parking lot. While Biff was waiting, Lou killed Gertrude, and put her in the back of his car to bury her. He told Biff that he had talked to his grandmother and said that she was still playing the slot machines.
- Lou stole the Grays Sports Almanac from Biff, and when he realized that it was the book that stated the winners, and not any methods that Biff had employed himself, he planned to kill Biff and bury him next to his grandmother. However, when he went to hit Biff with a tire iron, Biff caught it and killed him instead.
- Biff justified the murder in his mind based on the fact that Lou had killed his grandmother. He buried Lou, and took all of the money that was in his briefcase. With the money, he covered up the murder of Gertrude by paying to have a death certificate forged that stated she died of natural causes.
- Date unknown:
- At Hill Valley High School, Lorraine Baines offered her condolences to Biff for the loss of his grandmother, but Biff ruins things by asking her if she wanted to park in his car later.
- Biff is told by Stanford S. Strickland that he will have to repeat his senior year again. When he tries to bribe Strickland with money from Lou's suitcase, he is expelled from school. In response, Biff drops out.
- Back to the Future Part II
- Back to the Future: Biff to the Future