In the scene where Johnnie and Annabelle refill the water reservoir of the train, Marion Mack said in an interview many years later that she had no idea that she was supposed to get drenched. Buster Keaton had not told her what was supposed to happen, so the shock you see is genuine.
The first try at getting the cannonball to shoot out of the cannon into the cab caused the ball to shoot with too much force. To cause it to shoot into the cab of the engine correctly, Buster Keaton had to count out the grains of gunpowder with tweezers.
Buster Keaton wanted to use the real locomotive "The General", which was at the Nashville, Chattanooga, and St Louis Union Depot in Chattanooga, TN. The railroad initially permitted him to do so, even providing him with a branch line to film on. However, when it became known that the film was to be a comedy, the railroad withdrew permission and Keaton had to look elsewhere.
Based on a true incident during the Civil War. In April 1862 Union agent James J. Andrews led a squad of 21 soldiers on a daring secret raid. Dressed in civilian clothes, Andrews and his men traveled by rail into the Southern states. Their mission was to sabotage rail lines and disrupt the Confederate army's supply chain. At the town of Big Shanty, GA (now known as Kennesaw), the raiders stole a locomotive known as "The General". They headed north, tearing up track, burning covered bridges and cutting telegraph lines along the way. William Fuller and Jeff Cain, the conductor and engineer of "The General," pursued the stolen train by rail and foot. They first used a hand-cart (as Buster Keaton does in the film), then a small work locomotive called "The Yonah," which they borrowed from a railroad work crew, and finally a full-sized Confederate army locomotive called "The Texas," which pursued "The General" for 51 miles--in reverse. During the chase Confederate soldiers were able to repair the sabotaged telegraph wires and send messages ahead of the raiders. Andrews and his men were intercepted and captured near Chattanooga, TN, by a squad of Confederate troops led by Gen. Nathan Bedford Forrest (who, after the war, was one of the founders of the Ku Klux Klan). Tried as spies, Andrews and seven of his raiders were hanged (a special gallows was built to hold all eight men). The rest of the raiders were traded in a prisoner exchange. In 1863 the survivors of the mission were awarded the first Medals of Honor (Andrews and the raiders who had been hanged later received the medal posthumously). Although this film is a comedy, the incident was later filmed by Walt Disney as a drama, The Great Locomotive Chase (1956), with Fess Parker--a Southerner, born in Texas--as Andrews.
For the scenes with the opposing armies marching, Buster Keaton had the extras (which included 500 Oregon National Guard troops) wear the gray uniforms of the Confederacy and march in one direction past the camera, then he had them change uniforms to the Union blues and had them march past the camera in the other direction.
The failure of the original copyright holder to renew the film's copyright resulted in it falling into public domain, meaning that virtually anyone could duplicate and sell a VHS/DVD copy of the film. Therefore, many of the versions of this film available on the market are either severely (and usually badly) edited and/or of extremely poor quality, having been duped from second- or third-generation (or more) copies of the film.
Producer Joseph M. Schenck gave Buster Keaton $400,000 to make this film, so the production company moved with 18 freight cars of props and sets to Oregon. In the next two months the town of Marietta, GA, was built near the Oregon town of Cottage Grove.
There were three locomotives used in the film: one as "The General", one as "The Texas" and one for a spare. The spare engine had been originally intended to play The Texas, but the engine that ultimately got that role was found to be in better condition. The spare engine played the role of the Union engine up to the bridge scene, where it played The Texas as it crossed the bridge.
A number of celebrities have cameos in this film: Glen Cavender had been a hero in the Spanish-American War. Frederick Vroom had appeared earlier in Buster Keaton's The Navigator (1924) as the girl's father whose ship is hijacked. Keaton's former director of photography, Elgin Lessley, has a cameo as the Union general who gives the command to cross the burning bridge. Producer Louis Lewyn has a bit part as a soldier.
Florida State University commissioned composer Jeff Beal to write a brand-new soundtrack for this film. It was premiered by the University Philharmonia along with the original film playing just above the orchestra.
The trivia items below may give away important plot points.
The scene in which The Texas crashes through the bridge was the single most expensive shot of the entire silent movie era. The Texas itself remained in the river until WWII, when it was salvaged for scrap iron.
When the Texas goes over the burning bridge and plummets into the river, the looks of shock on the faces of the Union officers were real, because the actors who played them were not told what was going to happen to that train.