 Traffic increased in the early 1860s, so in 1863 and 1864, OSN added the "Nez Perce Chief", the "Webfoot", the "Owyhee" and the "Yakima", all built at Celilo on the upper Columbia, and the Mississippi-style side-wheeler "Oneonta" on the middle river.OSN also purchased the side-wheeler "New World" to work the lower Columbia.By 1878, OSN had added to its fleet the sternwheelers "Harvest Queen", "John Gates", "Spokane", "Annie Faxon", "Mountain Queen", "R.R.