What Are CFCs? CFCs are short for the compound, chlorofluorocarbon, which contain carbon, chlorine, and fluorine. Chlorofluorocarbons are more commonly referred to as CFCs or, when used for refrigeration, CFCs are also known as freon. Developed in the 1930s as a safe alternative to ammonia, usage of CFCs grew rapidly because of its usefulness and convenience throughout most of the 20th century.
Great Northern Railway 1893-1925 The first route over the pass was a series of switchbacks, with grades of up to 4 % on the West side and 3.5% on East side, was completed on January 6, 1893 (see photos below). To traverse a switchback the train has to travel to the end of the dead end spur, then the switch is thrown and engine reverses
The Pennsylvania Railroad was an American Class I railroad that was established in 1846 and was headquartered in Philadelphia, Pennsylvania. It was called the Pennsylvania Railroad because it was established in the state of Pennsylvania. The PRR was the largest railroad by traffic and revenue in the U.S. for the first half of the 20th 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 rai