No known biography of General Baldwin appears to be available at this time. It is known he was a brother of Leon Baldwin, once owner of Los Feliz Ranch, Contemporaries described him as "a typical southern gentlemen, an ex Confederate officer, a man of all around education, who was always immaculately dressed."

William Andrew Spaulding in his History and Reminiscences of Los Angeles City and County California wrote that "John M. Baldwin of the real estate firm of Baldwin and Beane was city surveyor for four months in 1875" and later served as city superintendent of streets in 1888.

The minutes of May 13, 1875, of what was the then City Common Council records that Mr. J. W. Baldwin tendered his resignation as City Surveyor. At the same time he informed the Council that the centerline of Spring Street has been established and the monuments properly placed as will appear on the records of his office. A map of the same has been furnished in pencil which as soon as it is copied on to (linen?) he will take pleasure in turning over to his successor.

"The center line of Fort Street has also been located and his successor will have no difficulty in establishing the monuments."