What two burgs were involved in May tenth celebration for Douglas?

This refers to the 10th of May in 1869 when, at Promontory Summit, Utah, the last spike for the "completion" of the transcontinental railroad was driven. The track was in fact not complete due to the fact that cargo and passengers had to be ferried across the Missouri river between Council Bluffs, Iowa and Omaha, Nebraska. (The two burgs.) A train from Ogden, Utah brought the band from Fort Douglas that played for the celebration at Promontory Summit.