Complex sentence: The magazine was first published in May 1903, as "The Red Book Illustrated", by Stumer, Rosenthal, and Eckstein, a firm of Chicago retail merchants; it changed its name to "The Red Book Magazine" shortly thereafter.
Split into simpler sentences: The magazine was first published in May 1903, as "The Red Book Illustrated", by Stumer, Rosenthal, and Eckstein, a firm of Chicago retail merchants. The name was changed to "The Red Book Magazine" shortly thereafter.