William first arrived in Utah with a party of '49ers headed for the California gold fields. (He had left a wife and two children in Illinois.) After brief exposure to the L. D. S. faith, Black converted. In Utah William met Bradford Leonard through his association with Brigham Young. Leonard had mill irons and leather for mill elevators that Young wanted William to take to Sanpete County. In Sanpete William lived in the home of Isaac Morley for two years. After that he returned to Illinois to get his family. While in Illinois William received a letter from Leonard asking him to help transport "a large stock of goods" to Utah. William bought seven wagons and twenty yoke of oxen and with Leonard, some hired hands and his family headed for Zion.
Black's company was originally was supposed to cross as a company of 10 with the James C. Snow company but they traveled separately from Snow's company. Black's company eventually caught up to the Robert Wimmer company. At that time, it was decided that 20 wagons from Wimmer's company would combine with Black's small company to continue on to Utah.
He is seen crossing the plains once more in 1856 with the Philemon C. Merrill Company.