and Pennsylvania railroads used Atlantics until the end of steam locomotive use in the 1950s, with some even being utilized in local freight and switching service. One of the best-known groups of s in the United States was the Pennsylvania Railroad's vast fleet of E class Atlantics, culminating in the PRR E6s class. Although Atlantics were sometimes used as mountain helpers prior to the First World War, they were not well-suited for mountain grades. They had large-diameter driving wheels, in some cases exceeding , which were adequate for trains. They tended to oscillate at higher speeds when the drive rods were connected to the rear pair of drivers. This was not standard practice in the U.S., however. The nation's biggest user of the type was the Santa Fe with 178 of the type. All of these were built with or drivers and the drive rods connected to the first pair of driving wheels. In 1905, Santa Fe engineer Charles Losee was widely reported to have driven Atlantic type 510, a 1904 balanced compound built by Baldwin, the from Cameron to Surrey in Illinois with a three car special train in one minute and thirty-five seconds. If that had been confirmed by a disinterested party, the per hour speed would have set a world record. These were never used on the road's Rocky Mountain grades; even on the flat plains of Kansas the Atlantics were soon overwhelmed by the weight of the newest all-steel, passenger cars. Despite their excellent performance, most were retired long before other locomotives of their era, and the few survivors wound up on light local trains. Milwaukee Road The Chicago, Milwaukee, St. Paul and Pacific Railroad (Milwaukee Road) used a streamlined Atlantic type on its midwestern Hiawatha passenger train service that was instituted in 1935. Four locomotives of the Milwaukee Road class A were constructed for this service in 1935. These s were reportedly the first steam locomotives ever designed and built to reach on a daily basis. These Atlantics with their distinctive streamlining shrouds were designed by industrial designer Otto Kuhler. Their calculated tractive effort was . An unusual feature of this locomotive was the drive onto the front coupled axle, which improved riding quality at speed. The locomotives were cross balanced and ran on drivers. They had an oil-fired grate and a rated boiler pressure of , which gave the boiler a high capacity in