Once the backlog of cargo was relieved by the Colorado, Johnson looked for ways to keep his boats from being idle. He knew that Brigham Young wanted to establish a route to the Mormon settlements in Utah from the sea up the Colorado River and that merchant interests had been interested in establishing trade with the Mormons by the river route since 1852 when the Uncle Sam came to the river. Additionally there was the claim that the river was navigable by steamboat as far as the Virgin River by the fur trapper Antoine Leroux who had successfully rafted down the Colorado from the Virgin River in 1837. Johnson was instrumental in getting Congressional funding for a military expedition to explore the Colorado River above Fort Yuma in 1856. Johnson lent Ives one of his men David C. Robinson as a pilot for the expedition. However, cut out of providing the steamboat for the 1857 expedition of Lt. Ives, Johnson at his own expense took the lead in the General Jesup heading up river first, exploring the river up to a point 8 miles into Pyramid Canyon to its first rapids, now under Lake Mohave, between Arizona and Nevada.