Green’s Dictionary of Slang

(US) prostitution.

1909		L.A. Herald 28 Feb. 4/1: [pic. caption] Frances Starr, in ‘The Easiest Way’.
1913		Day Book (Chicago) 29 Jan. 9/2: Filching the last penny from profits is filching it from girls’ wages [...] These women who toil at the clothing trades are [...] driven to the ‘easiest way’ by the women of America who buy, and who do not think as they buy!
1916		Day Book (Chicago) 19 Jan. 21/1: She had a profession [...] Nice persons, when they have a need to refer to it call it ‘the easiest way’.
1917		Arizona Republican (Phoenix, AZ) 21 Oct. 2/4: Laura Murdock, just as thousands of her sister unfortunates who have tried to live right in New York’s mad whirl, takles ‘The Easiest Way’.