Peg Entwistle reportedly immigrated to America, sailing from Liverpool aboard the S.S. Philadelphia in 1916, and settled in New York City. However, documents and photographs made available by the Entwistle family for a biography state that Entwistle and her father were in Cincinnati, Ohio, and New York City in early spring 1913. This information is also backed up in the Internet Broadway Database, and The New York Times, where Robert S. Entwistle is listed in the cast of several plays in 1913.

In December 1922, Robert Entwistle died, the victim of a hit-and-run motorist on Park Avenue and 72nd Street in New York City. Peg and her two younger half-brothers were taken in by their uncle, who had come with them to New York and was the manager of Broadway actor Walter Hampden.

By 1925, Entwistle was living in Boston as a student of Henry Jewett’s Repertory (now called the Huntington Theatre) and was one of the Henry Jewett Players, who were gaining national attention. Walter Hampden gave Entwistle an uncredited walk-on part in his Broadway production of Hamlet, which starred Ethel Barrymore. She carried the King’s train and brought in the poison-cup.

Entwistle, at age 17, played the role of Hedvig in a 1925 production of Henrik Ibsen’s The Wild Duck. After seeing the play, Bette Davis told her mother, “I want to be exactly like Peg Entwistle.” Some years later, Broadway actress and director Blanche Yurka sent a note to Davis asking if she would like to play Hedvig, and Davis sent word back that ever since she had seen Entwistle in The Wild Duck, she had known she would someday play Hedvig. Through the years, Davis said Entwistle was her inspiration to take up acting.

By 1926, Entwistle had been recruited by the New York Theatre Guild, and her first credited Broadway performance was in June of that year as Martha in The Man from Toronto, which opened at the Selywn Theatre and ran for 28 performances. Entwistle performed in ten Broadway plays as a member of the Theatre Guild between 1926 and 1932, working with noted actors such as George M. Cohan, William Gillette, Robert Cummings, Dorothy Gish, Hugh Sinclair, Henry Travers and Laurette Taylor. Her longest-running play was the 1927 hit Tommy, in which she starred with Sidney Toler, which ran for 232 performances and became the play for which she was most remembered.

In April 1927, Entwistle married actor Robert Keith at the chapel of the New York City Clerk’s office. She was granted a divorce in May 1929. Along with charges of cruelty, she claimed her husband did not tell her he had been married before and was father to a six-year-old boy, Brian Keith, who later became an actor.

The play The Uninvited Guest closed after only seven performances in September 1927; however, The New York Times critic J. Brooks Atkinson wrote, “Peg Entwistle gave a performance considerably better than the play warranted.”

She went on tour with the Theatre Guild between Broadway productions. Changing characters every week, Entwistle garnered some publicity, such as an article in the Sunday edition of The New York Times in 1927 and another in the Oakland Tribune two years later.

Aside from a part in the suspense drama Sherlock Holmes and the Strange Case of Miss Faulkner and her desire to play more challenging roles, Entwistle was often cast as a comedian, most often the attractive, good-hearted ingénue. In 1929, she told a reporter:

In early 1932, Entwistle made her last Broadway appearance, in J. M. Barrie’s Alice Sit-by-the-Fire, which also starred Laurette Taylor, whose alcoholism led her to two missed evening performances and refunds to ticket-holders. The show was cancelled, and in the aftermath, Entwistle and the other players were given only a week’s salary, rather than a percentage of the box office gross, which had been agreed upon before the show opened.

By May 1932, at the height of the Great Depression, Entwistle was in Los Angeles with a role in the Romney Brent play The Mad Hopes, starring Billie Burke, which ran from 23 May to 4 June at the Belasco Theatre in downtown Los Angeles. Florence “Flo” Lawrence, theatre critic for the Los Angeles Examiner, gave the production a very favorable review:

After The Mad Hopes closed, Entwistle won her first and only credited film role with Radio Pictures (later RKO). Thirteen Women stars Myrna Loy and Irene Dunne in a pre-Hays code, high-budget thriller produced by David O. Selznick and drawn from the novel by Tiffany Thayer. Entwistle played a small supporting role as Hazel Cousins. It premiered on 14 October 1932, a month after her death, at the Roxy Theatre in New York City, and was released in Los Angeles on 11 November to neither critical nor commercial success. By the time it was re-released in 1935, 14 minutes had been cut from the film’s original 73-minute running length. In 2008, Variety magazine cited Thirteen Women as one of the earliest “female ensemble” films.

On 18 September 1932, a woman was hiking below the Hollywoodland sign, when she found a woman’s shoe, purse, and jacket. She opened the purse and found a suicide note, after which she looked down the mountain and saw the body below. The woman reported her findings to the Los Angeles police and laid the items on the steps of the Hollywood police station.

Entwistle’s death brought wide and often sensationalized publicity. Her funeral was held at the W.M. Strathers Mortuary, in Hollywood, on 20 September. Her body was cremated and the ashes were later sent to Glendale, Ohio, for burial next to her father in Oak Hill Cemetery, where they were interred on 5 January 1933.

Dory Previn sang about Entwistle in the song “Mary C. Brown and the Hollywood Sign,” on her 1972 album of the same name.

Some have speculated that the 1977 Steely Dan recording “Peg” is about Entwistle; however, in 2000, during a question-and-answer session with fans, the band said the song was written about a real person but not Entwistle. In 2020, Steely Dan cofounder Donald Fagen said, “There’s no hidden meaning. We just wanted a dotted half note for that spot and Peg was short enough to fit with the music.”.

In 2014, roughly 100 people marked the anniversary of Entwistle’s death by gathering in the parking lot of Beachwood Market in Hollywood, to watch Thirteen Women on an outdoor screen. Proceeds from a raffle and from food and beverages sold at the screening were donated to the American Foundation for Suicide Prevention in Entwistle’s name.

In 2015, French songwriter and musician Benoit Clerc composed and released “Peg est mon nom” (“Peg is my name”), a ballad sung by Camille Saillant. The song imagines Peg Entwistle standing atop “The big white letter H” as she wonders whether she will be remembered after her death.

Ryan Murphy’s 2020 miniseries Hollywood revolves around the fictional production of a film, titled Peg, about Entwistle’s acting career and suicide.

The song “Gardenias” by Protest The Hero references the suicide of Entwistle as a symbol for the struggle of “making it” in Hollywood. The lyrics heavily feature alliteration on the letter “H” and contain several references to Entwistle’s death, including the height of the Hollywood sign and the discovery of her remains by a hiker. The song appears on the album Palimpsest, which was released on 18 June 2020.