Clara was born in 1855 in New Jersey, the daughter of Daniel and Martha Clayton. Her uncle, Ulysses S. Clayton, was a general in the American Civil War.
When Clara was 11, she caught diphtheria and was quarantined for three months, so her father bought her a telescope and put it next to her bed so she could see everything out the window. This ignited a love of science and astronomy that would stay with her for the rest of her life.
Little is known about her life between 1861 and 1885, except she became a schoolteacher and had been doing the job for some years before 1885. When she heard that the position of the new schoolteacher in Hill Valley was available, she decided to leave New Jersey behind and head out West to start a new life in California.
On September 4, 1885, Clara moved out to Hill Valley, California, taking up a job as a schoolteacher. But as no one had come to pick her up, she rented a horse and buckboard. However the horses were spooked by a snake and she died falling into Shonash Ravine, which was renamed Clayton Ravine in her memory. The story of her death became a legend among Hill Valley school children who had teachers they wished would also fall into the ravine.
These events were altered when Dr. Emmett "Doc" Brown arrived in 1885 in his DeLorean Time Machine. Doc volunteered to pick up Clara from the train station, where they met and fell in love at first sight. Sadly, within a week Doc was shot in the back by Buford Tannen, and died 2 days later. Clara helped pay for Doc's tombstone, engraving it with "Beloved Clara". Marty McFly found this tombstone in 1955 with the 1955 Doc (aged 35/41) and headed back to 1885 to save the 1985 Doc (aged 65/71) from being murdered.
As such, Doc did not go to pick up Clara at the station - if he never met her, he could never fall in love with her - and as before, Clara hired a horse. It was spooked by the snake, but luckily for Clara, Doc and Marty were around to save her life. Once again Clara and Doc fell in love at first sight, which caused problems for Marty who was anxious to get back home to 1985. Doc and Clara attended the Hill Valley festival on September 5, 1885 and spent the night watching the stars through her telescope. They discovered a common love for the novelist Jules Verne. Doc soon realized that he had to say goodbye to Clara and go back to the future. He tried telling her where he was going but she did not believe him and slapped him.
The next morning, September 7, Clara was on a train to San Francisco. However, after hearing about Doc from the man who was at the Palace Saloon with Doc all night, Clara stopped the train and ran back to town. Clara discovered that Doc was telling the truth after seeing the demonstration model on how the time machine was going to get back to the future. She jumped on a horse to catch up with Doc and Marty, who had "borrowed" a train to push the DeLorean up to 88 mph. Clara found the detached passenger cars of the locomotive they took, and hurried down the track to reach it. She caught up to the train on horseback and reached out for the ladder on the firewood car. Just as her gloved hand grasped it, the first "presto" log exploded, causing Clara to fly up in the air and land safely on the ladder.
Clara climbed up the ladder and saw Doc on the side of the train. She tried to get his attention, but he couldn't hear her because of the loud noise of the train. She continued to slowly crawl along the logs of firewood until the second presto log exploded, knocking her backward. She recovered and managed to get into the cab where she blew the train's whistle, thus alerting Doc and Marty to her presence. Clara proclaimed her love for Doc, prompting a discussion between him and Marty. Marty informed Doc that they were past the "point of no return," and Doc consequently decided he would take Clara with them to the future.
Doc convinced a hesitant Clara to climb out of the cab. She gave a look down at the churning wheels before mounting herself on the seat of the cab. She swung her legs out and over the seat to carefully step her high-heeled boots on the thin, precarious ledge. Doc approached Clara as she kept inching the tips of her boots along the ledge to his encouragements. Clara continued to come closer, grasping a metal bar with her gloved hands, and the lovers were soon close enough to reach one another.
Right as their hands were about to touch, the last presto log suddenly exploded, causing the metal bar Clara was holding on to broke, and her boots slipped off the ledge. However, Clara's fall was broken when her long dress became caught on part of the train. The dress began to rip from Clara's weight. With Clara's dress ripping more with each passing moment, Marty hurriedly sent Doc his hoverboard. Doc caught it and made his way over to Clara, grabbing her just as the dress tore completely from the metal knob. They hovered off into the distance as Marty watched and he was forced to go back to 1985 without them.
The DeLorean had been destroyed by a train once back in 1985 (Marty having gotten out in the nick of time) so he could not come back to 1885 to pick up Doc and Clara. As such Doc started work on a new time machine built into a steam train, as neither he nor Clara (who should have been dead) belonged in 1885. The two married on December 15, 1885 in a small ceremony. Since everyone believed that "Clint Eastwood" (Marty's chosen alias in 1885) perished in the ravine, in 1985, the ravine is called Eastwood Ravine, instead of Clayton Ravine (since Clara never perished).
Over the next 10 years, Doc and Clara worked on the train as their family grew. Clara gave birth to the couple's first son, Jules in 1886, followed by younger brother Verne in 1888. Eventually the time machinewas finished and the Brown family left the 1890s to travel to the future (where the train would be fitted with a hover conversion) and later to 1985 to visit Marty and his girlfriend Jennifer Parker, before departing for times unknown.