Locomotive, Steam, 4-8-2 Mountain M1

History: Under the Whyte notation for the classification of steam locomotives, 4-8-2 represents the wheel arrangement of four leading wheels, eight powered and coupled driving wheels and two trailing wheels. This type of steam locomotive is commonly known as the Mountain type.

One of the largest users in the United States was the Pennsylvania Railroad with 224 Class M1, Class M1a and Class M1b locomotives that were used mostly for fast freight service. A single prototype, #6699, was built in 1923 at the railroad's Altoona Works. It spent three years in testing, including all kinds of main line service as well as a session on the railroad's static test plant. Having received favorable reports, a further 200 were ordered from commercial locomotive builders; 175 from the Baldwin Locomotive Works and 25 from Lima Locomotive Works. Breaking with the PRR tradition of random locomotive numbering, these were numbered in a solid block from #6800-#6999.

In 1930 100 more were ordered; this class M1a had several improvements. Instead of separate cylinder block and smokebox saddle castings, the M1a had a one-piece casting (first seen on the K5 Pacific) with inside steam delivery pipes, instead of the outside, visible pipes of the M1. A Worthington feedwater heater was installed, with a boxlike mixing chamber behind the stack. Twin cross-compound air compressors were hung next to each other on the left side, instead of the single compressor of the M1. The M1a locomotives had larger tenders than the previous locomotives.

From Wikipedia

Railroad/Company: The Pennsylvania Railroad (reporting mark PRR) was an American Class I railroad, founded in 1846. Commonly referred to as the "Pennsy," the PRR was headquartered in Philadelphia, Pennsylvania.

The PRR was the largest railroad by traffic and revenue in the U.S. for the first half of the twentieth century. Over the years, it acquired, merged with or owned part of at least 800 other rail lines and companies. At the end of 1925, it operated 10,515 miles of rail line; in the 1920s, it carried nearly three times the traffic as other railroads of comparable length, such as the Union Pacific or Atchison, Topeka & Santa Fe railroads. Its only formidable rival was the New York Central (NYC), which carried around three-quarters of PRR's ton-miles.

At one time, the PRR was the largest publicly traded corporation in the world, with a budget larger than that of the U.S. government and a workforce of about 250,000 people. The corporation still holds the record for the longest continuous dividend history: it paid out annual dividends to shareholders for more than 100 years in a row.

In 1968, PRR merged with rival NYC to form the Penn Central Transportation Company, which filed for bankruptcy within two years. The viable parts were transferred in 1976 to Conrail, which was itself broken up in 1999, with 58 percent of the system going to the Norfolk Southern Railway (NS), including nearly all of the former PRR. Amtrak received the electrified segment east of Harrisburg.