With two outs in the second inning of an eventual 1-0 loss to the Giants, Cardinals’ southpaw Max Lanier walks Monte Irvin, gives up a double down the right-field line to Willie Mays, and then intentionally walks Hank Thompson to load the bases. The St. Louis lefty will get out of the early jam by striking out opposing pitcher Dave Koslo, but the frame will mark the first time in major league history a trio of black players occupies three bases at the same time.

This Day In Baseball

On June 3, 1951 — With two outs in the second inning of an eventual 1-0 loss to the Giants, Cardinals’ southpaw Max Lanier walks Monte Irvin, gives up a double down the right-field line to Willie Mays, and then intentionally walks Hank Thompson to load the bases. The St. Louis lefty will get out of the early jam by striking out opposing pitcher Dave Koslo, but the frame will mark the first time in major league history a trio of black players occupies three bases at the same time.

Source
Baseball Reference June 3