time. In the United States, the 2-6-0 was already the common design for this sort of engine, and these imports were to be very influential in introducing the wheel arrangement to the United Kingdom. At the time of the Railways Act 1921 Grouping in 1923, 2-6-0 locomotives were operated by the Caledonian Railway (34 class, 1912), the Glasgow and South Western Railway (403 class, 1915), the GNR (H2, H3 and H4 classes, 1920), the Great Western Railway (2600 and 4300 classes of 1900 and 1911 respectively), the London, Brighton and South Coast Railway (K class, 1913) and the South Eastern and Chatham Railway (N class, 1922). Several of these designs continued to be built by the Big Four after 1923, and several new and successful designs were introduced so that the 2-6-0 became the principal type for medium-loaded mixed-traffic duties. Notable new designs included the Southern Railway's U class (1928), the London Midland & Scottish Railway’s LMS Hughes Crab (1926), the LMS Stanier Mogul (1934), the LMS Ivatt Class 2 2-6-0 (1946), the LMS Ivatt Class 4 (1947), the London and North Eastern Railway’s LNER Class K4 (1937) and the LNER Thompson/Peppercorn Class K1 class which were built in 1949–50 after the nationalisation of British Railways. British Railways continued to build the Ivatt and Thompson/Peppercorn designs and then introduced three standard designs, based on the Ivatt classes. These were the BR Standard Class 2 2-6-0 in 1952, the BR Standard Class 3 2-6-0 in 1954 and the BR Standard Class 4 2-6-0 in 1952. 2-6-0 locomotives continued to be built until 1957 and the last ones were withdrawn from service in 1968. United States The first true with single-axle swivelling leading trucks were built in the United States in 1860 for the Louisville and Nashville Railroad. The New Jersey Locomotive and Machine Company built their first 2-6-0 in 1861, as the Passaic for the Central Railroad of New Jersey. The Erie Railroad followed in 1862 with the first large order of this locomotive type. In 1863, Rogers Locomotive & Machine Works built more for the New Jersey Railroad and Transportation Company. The Baltimore & Ohio (B&O) no. 600, a Mogul built at the B&O's Mount Clare Shops in 1875, won first prize the following year at the 1876 Centennial Exposition in Philadelphia. It is preserved at the B&O Railroad Museum, housed in the former Mount Clare shops in Baltimore. Well