Pamela was born to Willard "Digger" Barnes (real father: Hutch McKinney) and Rebecca Barnes. She had an older brother Cliff. She was told by Digger that her mother died when she was just a little baby. Pam and Cliff were brought up by Digger's sister Maggie Barnes Monahan, living in a rundown part of Dallas. Her aunt was a widower and religious fanatic and Pam loved her dearly.Pam was also close with Maggie's son , her cousin Jimmy Monahan.As time went by Digger visited his children less and less. When he did see them, all he seemed to talk about was his rivalry with, and hatred of, Jock Ewing.
Pam met a young soldier named Edison Haynes, who declared his love for the fifteen year old girl. Ed whisked her across the border to Juarez to get married, but Digger found them before they had time to consummate the marriage and dragged Pam back to Dallas. Ed was shipped off to Vietnam the next day and Digger had the marriage annulled.
Soon after moving to Southfork, Bobby's brother J.R. accused her of being a spy for her brother, Clifford "Cliff" Barnes, who was building a case against Ewing Oil. She was accused of leaking a very important Red File to Cliff. Bobby vigorously defended her, and the family eventually found out that Pam was innocent.
In Episode #5 Season 1, Pam announced that she was expecting a child; all the Ewings, except J.R. and Sue Ellen, forgave her for being a Barnes. The family's joy was terminated, however, when she lost the child, after a fall from the loft in the barn, because of J.R.
As Pam was beginning to recover from the trauma, Ed Haynes turned up in Dallas to claim that they were still married. J.R. gleefully brought the news — that Pam was a bigamist — to the family dinner table. Though Pam hastened to explain to the Ewings that the marriage had been annulled, the papers testifying to that fact had mysteriously disappeared. Eventually Pam was cleared, and Haynes was found to be a blackmailer. Pamela kept a wary eye on J.R., after that. His desire to get her out of the family was all too apparent.
Trouble was forever being generated by J.R., as he openly despised Pam.
In 1979, Pam was told by Digger's doctor that Digger was a carrier of Neurofibromatosis, and that she and Cliff, as his children, were carriers; as neurofibromatosis is a disease that could be fatal to infants, the doctor strongly advised them never to have children. Shortly thereafter, Pam discovered she was pregnant. Then tragedy struck. A rattlesnake scared Pam's horse and she was thrown, causing a miscarriage. Later she found out that she was not Digger's daughter and thus was not a carrier of the disease. Then she was told that, after two miscarriages, she could not bear children. Pam for a time transferred her maternal feelings to J.R. and Sue Ellen's son John Ross.
In 1980, Pam watched Digger painfully and slowly die as a result of his years of alcoholism. Overwhelmed by a sense of loss, she pushed to find out more about her mother. She developed a notion — a dream born out of grief — that perhaps her mother wasn't dead after all. Then a private investigator turned up evidence that her mother had not died as Digger had said.
Meanwhile, Bobby had taken over Ewing Oil while J.R. was convalescing after being shot. Pam watched her husband get deeper and deeper into the heart of business in an effort to prove himself, and she took note of Bobby's instinctive attraction to power, which she realized might be dangerous to their marriage.
Pam's private investigator located a woman he believed to be Pam's mother. But the woman, a society matron from Houston named Rebecca Wentworth, flatly denied that she was Pam's mother. Eventually Rebecca broke down and confessed that she was indeed Pam's mother. The baby issue continued to haunt Pam, after the doctors had told her that she could not carry a child past the third month of pregnancy. Her depression culminated in near-fatal tragedy: Pam tried to kill herself by jumping off the top of the place of her employment, The Store. However, Bobby got there in time to stop her, but it was clear that Pam was in need of psychiatric help. She was admitted to a psychiatric hospital where she could get the help she needed.
On a surprise visit to Southfork, Pam walked through the front door and saw Bobby with the most precious little baby boy in his arms. In soaring spirits, Pam quickly settled into her life as Christopher's mother, while Bobby continued with the adoption proceedings.
She and Bobby grew closer during this period. In May of 1982 Bobby finally told Pam about Jeff Faraday, Kristin Shepard and the fact that J.R. could be Christopher's father. Pam was shocked that Bobby had kept this news from her all this time, but she didn't hesitate to jump right in and fly to California with him to find the truth, prepared to fight whoever she had to keep her son.
The Ewings formally adopted Christopher in the fall of 1982, and the little Ewing family seemed on good ground. However, the revival of the Barnes-Ewing feud placed tremendous strain on Bobby and Pam's marriage. And the contest between Bobby and J.R. for Ewing Oil compounded the stress. Pam wanted to leave Southfork, to leave Texas if they had to, but Bobby refused.
Tension continued to escalate as Miss Ellie attempted to break Jock's will and stop the contest that was tearing the family apart. Bobby became angry with Pam when she sided with Miss Ellie, as he had sided with J.R. on the issue. As emotions rose at Southfork, Pam leaned more and more on her mother for support.
As Rebecca was leaving for Houston on business, the Wentworth jet was involved in a midair collision. Rebecca died as a result of her injuries. Pam was devastated — and angry — blaming the contest between J.R. and Bobby for her mother's death. Pam left Bobby and they divorced in the fall of 1983.
By 1985, Bobby realized he wanted to be back with Pam, and tried to convince her to remarry him. Eventually, she agreed, and they spent that night together. Pam went on to make television history by dreaming an entire season of the series, during which Bobby was tragically cut down by a car and died hours later, leaving Pam mortified and heartbroken. Pam awoke and found Bobby in the shower, alive and well.
Pam received good news at the end of 1987: she was finally able to conceive a baby, after confirming that there would be no health risks involved. However, she never got that chance. While calling her husband to tell him the good news, she was in a massive auto accident where she hit an oil tanker and was severely burned in a subsequent fire. While recovering from her burns, she decided get away from the Ewings and everyone else, including her son, disappear and divorce Bobby for a second time.
She resurfaced using her late Aunt Maggie's last name Monahan and going by the name Pamela Monahan (being played by Margaret Michaels) for a small cameo in the following season. Tracked down by her brother Cliff, Pam had undergone plastic surgery. She told him that she was also involved with her doctor and that she wished to have no further ties to Dallas. Pam later explained to the doctor that she lied because of having an unspecificed, fatal illness, and that she did not want to burden Bobby or Christopher with the ordeal of losing her all over again.