 During the 1860s , gold strikes in Montana , Colorado , Wyoming and northern Utah attracted another wave of <unk> to the region . Although some freight was hauled overland , most transport to and from the gold fields was done through the Missouri and Kansas Rivers , as well as the Snake River in western Wyoming and the Bear River in Utah , Idaho and Wyoming . It is estimated that of the passengers and freight hauled from the Midwest to Montana , over 80 percent were transported by boat , a journey that took 150 days in the upstream direction . A route more directly west into Colorado lay along the Kansas River and its tributary the Republican River as well as pair of smaller Colorado streams , Big Sandy Creek and the South Platte River , to near Denver . The gold rushes precipitated the decline of the Bozeman Trail as a popular emigration route , as it passed through land held by often @-@ hostile Native Americans . <unk> paths were blazed to the Great Salt Lake near <unk> , Utah during the gold rush period , which led to the large @-@ scale settlement of the Rocky Mountains region and eastern Great Basin . 
