Question: What year did the Southern Pacific class AC-9 begin running between Alturas, CA and Nevada's fifth most populous city?

<P0-S0> The AC-9 was one of two Southern Pacific Railroad's articulated steam locomotive class that ran smokebox forward after 1920. <P0-S1>  Twelve AC-9 class locomotives were built by Lima in 1939 and were Southern Pacific's largest and heaviest steam engines, partly a consequence of low quality coal these engines were designed to burn. <P0-S2>  The AC-9s were partially streamlined (the only articulated steam engines to be so equipped), having "skyline casings" inspired by Lima's GS series of 4-8-4's, also made for Southern Pacific, and were equipped with coal tenders, unlike the cab forwards. <P0-S3>  The wheel arrangement was 2-8-8-4, which was nicknamed "Yellowstone". <P0-S4>  Between 1939 and 1952, all the twelve AC-9 engines were in service between Tucumcari, New Mexico, El Paso, Texas, and Tucson, Arizona, where they mainly pulled freight trains and occasionally also passenger trains such as the "Golden State Limited". <P0-S5>  In 1952, they were converted to burn oil instead of coal, and moved to Southern Pacific's Modoc line between Sparks, Nevada, and Alturas, California, where they worked in freight service from 1953 until retirement in 1956. <SEP> <P1-S0> Sparks is a city in Washoe County, Nevada, United States. <P1-S1>  It was founded in 1904 and incorporated on March 15, 1905, and is located just east of Reno. <P1-S2>  The 2010 U.S. Census Bureau population count was 90,264. <P1-S3>  It is the fifth most populous city in Nevada. <P1-S4>  It is named after the late Nevada Governor John Sparks, a member of the Silver Party. <SEP> <P2-S0> The Butte County Railroad was a 31.5 mi class II railroad that ran from a connection with the Southern Pacific Railroad at Chico, California to the Diamond Match Company lumber mill at Stirling City. <P2-S1>  The railroad operated from 1903-1915 and then became the Southern Pacific's Stirling City Branch. <P2-S2>  From 1915 until abandonment in the 1970s the line was operated as the Southern Pacific's Stirling City Branch. <P2-S3>  The Chico and Northern Railroad was a non-operating subsidiary holding company of the Southern Pacific Railroad that was created to acquire a 32.31 mile line from Chico - Stirling City from the Butte County Railroad. <P2-S4>  Upon acquiring the line, Chico & Northern immediately leased the line back to the Butte County Railroad. <P2-S5>  The Chico & Northern was dissolved into Southern Pacific in 1912 and never operated any of the line. <SEP> <P3-S0> Sierra Nevada was a steel-hulled steam-powered passenger ferry operated on San Francisco Bay. <P3-S1>  The ferry was built for the Western Pacific Railroad as "Edward T. Jeffery" in 1913 and subsequently renamed "Feather River". <P3-S2>  The ferry offered connecting service to San Francisco for Western Pacific train passengers arriving in Oakland, California. <P3-S3>  The ferry was sold to Southern Pacific Transportation Company when Western Pacific began using Southern Pacific's Oakland ferry facilities in May, 1933. <P3-S4>  Southern Pacific renamed the ferry "Sierra Nevada" and placed it in commuter service between San Francisco and Alameda, California until that route was discontinued in 1939. <P3-S5>  The ferry was leased to the Key System for the Golden Gate International Exposition on Treasure Island from 1939 through 1940. <P3-S6>  In 1942, the ferry was requisitioned by the federal government to carry shipyard workers from San Francisco to Richmond Yard 1 through World War II. <P3-S7>  The Richmond-San Rafael Ferry Company purchased the ferry in 1947 and rebuilt it to carry automobiles between Richmond and San Rafael until the Richmond–San Rafael Bridge opened on 1 September 1956. <P3-S8>  The ferry was then towed to San Pedro, Los Angeles where she sank in 1978.