Allegedly born in 1845 (or before) in Texas, Bill was the youngest of a very large family. At that time she was known as Billie, and while her family's wagon was crossing the Pecos River the infant Billie tumbled out of the back and down the bank. She drifted down river and when she finally came to a stop, the scent of food urged the little baby to crawl toward it. There she found a pack of coyotes. The coyotes were confused by the human child, but seeing as it crawled right up unafraid they decided to raise it. For the first thirteen years of her life she lived as a coyote, running, hunting, and sleeping with the pack. She was a friend to all animals, having come to an understanding with them. It was only on her fourteenth birthday that she was found by a man who turned out to be her older brother who recognized her. He convinced Billie that she was not a coyote and taught her human language before taking her back to civilization.
With the smarts of a human, the instinct of a coyote, and an understanding of nature deeper than either, Billie changed the Wild West. She taught the people who to herd cattle. While playing with a snake she created the first lasso. She fashioned the first spurs, and settled property disputes by inventing the cattle prod. She scared away bandits and outlaws with her sharp aim and impressive strength. She became the boss and protector of several ranches at a young age due to her talent, and people looked up to her.
As she came into adulthood her prowess grew into the fantastic. By now Billie could outrun any horse, and had taken to riding wild cougars instead. During a drought the people pleaded with Billie to do something, and she sniffed out a cyclone several states away. She rode towards it on the back of her wild cat and with her trusty living lasso, the snake known as Shake, she captured the storm and pulled herself on top of it. She squeezed it until the water trapped inside flew out and rained down on the West. On her way back to Texas she saved a town from a lake monster, grappling with it for several days until she ultimately came out on top. Her fame was well established at that point. But there were two things that Billie longed for.
The first was a horse. The mountain lions were ferocious, but were no proper steed for a cowboy. There was only one horse that could outrun Billie: Widow-Maker, a pitch black stallion with a yellow mane like lightning. He was named as such because he had killed every man that attempted to break him. This horse ate dynamite and made craters when it bucked, and it was this horse that Billie set her eyes on. The struggle was intense, but after days of battling Widow-Maker Pecos Billie was victorious. She promised Widow-Maker that no one else would ride him, and the two became friends.
The second thing she longed for was someone to share her life with. Billie needed someone that understood her. She was caught between her human life and her coyote family. She went out several times a week to live the simple life among animals. It was on one such occasion where she was snatching up fish with her mouth alongside her coyote pack that she spotted a woman floating down the river on the back of a giant catfish. For Billie it was love at first sight. The woman's name was Slue-Foot Sue, and over the next few weeks Billie did everything in her power to court her, including shooting all of the stars from the sky save one. Eventually Sue agreed to marry Billie. Their wedding was to be a simple one out in the wilderness with all of their families, man and animal included. After their wedding Sue asked if she and Billie would ride away into the sunset together. Billie agreed that they should, but Widow-Maker had grown jealous of Sue. When Billie lifted Sue onto Widow-Maker's saddle and broke her promise to the horse, Widow-Maker used his incredible power and bucked her off. Sue went flying, landed on her bustle, and then flew up even higher. So high that she got stuck on the moon.
Billie cried and screamed and howled. The coyotes howled too, and they continued to howl at the moon for Sue ever since.
The heartbroken cowboy eventually rode off alone. When she returned to town she continued to work diligently for the people, but it was said she never loved again after that night. She mixed human words with her howls to the moon, and the other cowboys emulated her, creating those lonesome drawling tunes they came to be known for. Billie never was able to make it up to the sky to be with Sue. Assuming that Sue had eventually died on the moon, Billie would eventually join her in the after life - but being as tough as she was, death did not come to her for many years. Only when in her old age a city man came into town with pristine hat and boots and a fake accent did she die - from laughter at the sight.
Over multiple re-tellings of her legendary exploits, "Billie" eventually became "Billy," and then finally "Bill." The name and deeds of "Pecos Bill" endured, but the name shortening seems to have misconstrued her original gender over time. She doesn't seem to mind at all, keeping the "Bill" moniker for ease.
