Neun was born in Baltimore, Maryland. Although never an everyday player (he never played more than 97 games a season), Neun entered baseball immortality on May 31, 1927 against the Cleveland Indians, when he caught a line drive from Homer Summa, stepped on first to retire Charlie Jamieson, and despite shouts from his shortstop to throw him the ball, raced towards second base to retire Glenn Myatt, completing the seventh unassisted triple play in MLB history, and the first such play to end a game. Neun became the second, and most recent, first baseman to accomplish the feat. It came one day after Jimmy Cooney of the Chicago Cubs turned his own unassisted triple play.