Notable Maryland resident Captain William B.S. Powell brought in stock from other states in the 1910's to improve the height of his ponies living on the Maryland end of Assateague. One of the breeds he introduced was Hackneys. Powell considered the experiment a failure as the Hackneys didn't breed as rapidly as the native ponies. While his ponies resided in Maryland there intermingling as was no fence at the time. Clarence Beebe bought some of Powell's ponies for his herd in 1942.