The Л (L) was the only Pacific tender locomotive in Russia. It was built by Putilov for the Vladikavkas Railway that needed a more powerful express locomotive for their line between Rostov and Vladikavkas. Designed by Vazlav Lopushinski (hence the designation L), it had four cylinders to decrease the stress for the rails. All four cylinders worked on the second driving axle. They were fired with oil, or naphtha as it is referred to in Russian sources. Later they were converted to coal burning.

18 locomotives were built for the Vladikavkas between 1914 and 1918. When the October Railway between Moscow and Leningrad (St. Petersburg) needed similar locomotives, 48 more were built between 1923 and 1926. These were transferred to the Vladikavkas in 1937 when the October Railway had received new locomotives. From 1947 they were designated Л^П (L^P) when the new Л freight locomotives had been introduced. Their withdrawals came in the fifties.