Green’s Dictionary of Slang

1. the west coast of America, esp. Los Angeles [the Pacific Coast has been thus known since the mid-19C, but the current use refers spec. to Los Angeles, the home of the film and rock industries].

1904		Number 1500 Life In Sing Sing 261: I went to the coast with a mob of paper-layers, but graft was on the fritter.
1927		D. Hammett ‘The Big Knockover’ Story Omnibus (1966) 282: How’d you like to pick up a piece of change out on the Coast?
1939		Goodman & Kolodin Kingdom of Swing 80: [I]t was the general opinion in the band that we ought to have a vacation, and that California was the place to have it. [...] Then we hit out for the coast again, and got there around July first.
1947		Chicago Sun 13 July 2/2: He was [...] defeated, it is true, but a big figure on the Coast [DA].
1950		‘Josephine Tey’ To Love and Be Wise 17: ‘[P]hotography. I spend most of the winter on the Coast, doing people.’ ‘The Coast?’ ‘California’.
1960		C. Cooper Jr Syndicate (1998) 3: I cound’t see the sense in Lou Pulco sending me all the way to the Coast.
1967		Sat. Night (Can.) July 41: It’s nonsense to listen to most good west coast rock unless you’re prepared to let yourself break out emotionally and just wallow around in the sound, a cathartic procedure that’s currently known on the coast as ‘freaking out’.
1972		E. Shrake Strange Peaches 209: ‘I’ve just stopped off from the Coast and I’m taking the red-eye to New York’.
1984		D. Jenkins Life Its Ownself 73: T.J. Lambert said he would fold me up like a taco if I didn’t stop in Fort Worth on my way out [from New York City] to the Coast.
1993		R. Firestone Swing, Swing, Swing 37: [T]hey decided [...] to look around for some good local talent they could break in on the Coast.

2. the Atlantic coast, to inhabitants of the Pacific seaboard.

1960, 1975

Wentworth & Flexner DAS.