[3] After graduation, she briefly worked as a teacher before quitting to pursue a career as a newspaper reporter.

[2] She began her professional newspaper career at The Salt Lake Herald after convincing the city editor to break with tradition and hire their first female reporter.

She went back to the Daily News as their Los Angeles correspondent when her former editor was having trouble covering a story in Hollywood.

Muir knew several mobsters, including Bugsy Siegel, who she claimed had threatened her over "what she had written about him"[6] during his trial for the murder of Harry Greenberg in 1941, saying "You think because I'm locked up here a punk like you can write anything you please ... Maybe you won't be using that typewriter anymore.

"[6] After Siegel's murder on 20 June 1947, Muir (who had spoken to Siegel earlier that day; he had called "to thank her for a favourable review"[7] of a show at his Flamingo Hotel) was "one of the first reporters at the scene";[8] noticing his left eyeball, which "had been blasted out of his head",[8] lying on the floor, she allegedly "picked up the sliver of flesh from which his long eyelashes extended.

"[8] Muir was also injured during an attempted assassination of mobster Mickey Cohen at Sherry's restaurant on the Sunset Strip at 3:55 a.m. on July 20, 1949.