The Central Branch Union Pacific Railroad was a railroad in the U.S. state of Kansas. Originally planned as a line from Atchison west into Colorado, and given federal land grants by the Pacific Railway Act of 1862 as one of the branches of the Union Pacific Railroad, it was left with a hanging end at Waterville, Kansas when the Union Pacific Railway, Eastern Division, with which it was to connect, changed its route. The line was acquired by the Union Pacific through a stock purchase by Jay Gould and leased to the Missouri Pacific Railroad in 1880. In 1909 the Central Branch was merged into the Missouri Pacific; the latter company came back into the Union Pacific system in 1982. In 1991 the remaining trackage west of Frankfort was leased to the Kyle Railroad.
Despite its name, the Central Branch Union Pacific was not associated with the Union Pacific until 1880; it was to be one of several eastern branches of the First Transcontinental Railroad, of which the Union Pacific constituted the main line between Council Bluffs, Iowa/Omaha, Nebraska and Ogden, Utah where it connected with the Central Pacific Railroad.
The Kansas Territorial Legislature incorporated the Central Branch as the Atchison and Pike's Peak Railroad in February 1859, with the power to build from Atchison, on the Missouri River, west to the Kansas-Colorado line in the direction of Pike's Peak or Denver. Through an 1862 treaty between the Kickapoo Indians and U.S. government, part of that tribe's land was sold to the railroad company. It acquired more land from the land grant provisions of the Pacific Railway Act of 1862, which included a line to be built by the Hannibal and St. Joseph Railroad of Missouri, extending west from Atchison. The west end of this branch would be at an intersection with the Leavenworth, Pawnee and Western Railroad, a planned connection from Kansas City to the main transcontinental line. The company would only receive land for the first 100 miles (160 km) from Atchison. The Hannibal and St. Joseph transferred its rights under the act to the Atchison and Pike's Peak in January 1864. Construction began in 1865, and the line was completed from Atchison west for 40 miles (64 km) in January 1867, and the rest of the 100 miles to Waterville in January 1868. The company changed its name to Central Branch Union Pacific Railroad in January 1867, better reflecting its purpose.