1907 as graphing of U.S. Southern pronunciation of Mrs. or Miss; 1972 as standard pronunciation of Ms.
Examples from the Web for miz
Just come and have a talk with Miz T. She'll straighten you around all right.The Gold Girl|James B. Hendryx
"So glad to hear you say that, Miz Mayfield," Margaret replied.The Starbucks|Opie Percival Read
Miss Betty, she walkin' in her gyahden an' Miz Tanberry fan' on de po'ch.The Two Vanrevels|Booth Tarkington
Miz Gormley never fitted me to nothin yet, returned Mr. Parlow grimly, less twas a suit of gossip.Carolyn of the Corners|Ruth Belmore Endicott
That Miz Parsons had no business to give ye five thousand dollars for gettin back her necklace from the Gypsiesa gal like you!Ruth Fielding In the Saddle|Alice B. Emerson