The Mormon Pioneers traveled to the Salt Lake Valley in 1847.  The first group, the Vanguard Group, consisted of 143 men (three of whom were black, two of those Priesthood holders), and two children.  They averaged between 14 and 20 miles a day.  From Fort Bridger, WY, they followed the way taken the previous year by the Donner Party.  The Donner Party had forged a trail, without which, the Mormon Pioneers might have perished because they then would have not arrived in the Salt Lake Valley until perhaps early September, too late to plant and harvest a crop.  Along the way, the Mormon Pioneers invented the modern odometer.