The Sioux City and Pacific Rail Road was a railroad in the U.S. states of Iowa and Nebraska. Built as a connection from Sioux City to the Union Pacific Railroad at Fremont, it became part of the Chicago and North Western Railway system in the 1880s, and is now a main line of the Union Pacific (UP). The east-west portion from Fremont to Missouri Valley is the Blair Subdivision, carrying mainly westbound UP trains (most eastbounds use the Omaha Subdivision), and the line from California Junction north to Sioux City is the Sioux City Subdivision.