Green’s Dictionary of Slang

(US) Saint Louis, Missouri.

1891		New Ulm Wkly Rev. (MN) 2 Sept. 4/1: Second prize at Illinois State fair [...] first at French Government Show at St Loo.
1893		Highland Recorder (Monterey, VA) 1/3: The ‘St Louie’ pronunciation will never cause anyone to forget why the city was named St Louis.
1899–1900		C.L. Cullen Tales of the Ex-Tanks 161: It takes dogs to win races in St. Loo, all correct.
1902		C.L. Cullen More Ex-Tank Tales 133: ‘What for St. Loo?’ says I to myself.
1913		University Missourian (Columbia, MO) 3 June 10/3: I was deeply [...] chagrined by the low stuff that the St Looie Sympathy band handed out.
1919		A. Baer Two & Three 18 Apr. [synd. col.] All the St Louis cops know about a bevy of St Looey crooks is that they wore raincoats and mean expressions.
1921		Eve. Public ledger (Phila., PA) 14 June 20/1: The St Looie players admitted the umpire was correct.
1959		J. Blake letter 30 Dec. in Joint (1972) 153: They’re rich, and influential around St. Loo.
1990		S. Morgan Homeboy 296: St. Looie for an earful of the blues, Alaska for a midnight suntan.