The sole original DGA-6 was constructed in 1934 in the defunct factory of the American Eagle-Lincoln Aircraft based at Fairfax Airport in Kansas City, Missouri.

The fuel capacity of the four-seat Mister Mulligan made the difference in the Bendix race, as Howard and Israel beat Roscoe Turner by less than a minute, thanks to two fewer fueling stops in the race from Burbank, California, to Cleveland, although Turner's 1,000 hp (750 kW) Pratt & Whitney R-1690 Hornet on his Wedell-Williams Model 44 racer gave him the power advantage.

By the end of the week, Howard and his DGA-6 replaced Wedell-Williams as the rising star of aviation by upsetting defending champion Turner in the Thompson race after he was forced out.

The next year, Howard and his wife Maxine were injured when Mister Mulligan lost a propeller blade and crash-landed near Crownpoint, New Mexico during the latter stages of the 1936 Bendix (New York–Los Angeles) race.

The misfortunes of Howard and Turner opened the way for Arkansan Louise Thaden in her Beechcraft Model 17 Staggerwing to become the first woman to win a national air trophy.

Thirty-four years after the accident, racing enthusiast, Bob Reichardt tracked down Mister Mulligan's crash site and was surprised to find most of the parts were still in usable condition, protected by local dry, mountain climate.

[6] With the salvaged parts as patterns, Reichardt was able to recreate Mister Mulligan, but was killed in 1977[7] while performing a timed run over the Tonopah, Nevada dry lake.