Track gauge in the United States

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Track gauge
By transport mode
Rapid transit Tram Miniature Scale model
By size (list)
Minimum   Fifteen inch 381 mm (15 in)   Narrow   600 mm 600 mm (1 ft 11+5⁄8 in) Two foot 610 mm (2 ft) Two foot three inch 686 mm (2 ft 3 in)   750 mm 750 mm (2 ft 5+1⁄2 in) Bosnian gauge 760 mm (2 ft 5+15⁄16 in) Two foot six inch 762 mm (2 ft 6 in)   Swedish three foot 891 mm (2 ft 11+3⁄32 in) 900 mm 900 mm (2 ft 11+7⁄16 in) Three foot 914 mm (3 ft) Italian metre 950 mm (3 ft1+13⁄32 in)   Metre 1,000 mm (3 ft 3+3⁄8 in)   Three foot six inch 1,067 mm (3 ft 6 in)   Four foot 1,219 mm (4 ft)   Four foot six inch 1,372 mm (4 ft 6 in)   1432 mm 1,432 mm (4 ft 8+3⁄8 in)   Standard 1,435 mm (4 ft 8+1⁄2 in)   Broad   Italian broad gauge 1,445 mm (4 ft 8+7⁄8 in) Dresden gauge 1,450 mm (4 ft 9+3⁄32 in)   Leipzig gauge 1,458 mm (4 ft 9+13⁄32 in)   Toronto gauge 1,495 mm (4 ft 10+7⁄8 in)   1520 mm 1,520 mm (4 ft 11+27⁄32 in) Five foot 1,524 mm (5 ft)   Pennsylvania gauge 1,581 mm (5 ft 2+1⁄4 in) Pennsylvania gauge 1,588 mm (5 ft 2+1⁄2 in) Five foot three inch 1,600 mm (5 ft 3 in)   Baltimore gauge 1,638 mm (5 ft 4+1⁄2 in)   Iberian gauge 1,668 mm (5 ft 5+21⁄32 in) Five foot six inch 1,676 mm (5 ft 6 in)   Six foot 1,829 mm (6 ft)   Brunel 2,140 mm (7 ft 1⁄4 in)   Breitspurbahn 3,000 mm (9 ft 101⁄8 in)
Change of gauge
Bogie exchange Break of gauge Dual gauge Conversion list Variable gauge
By location
North America South America Europe Australia

Originally, various track gauges were used in the United States. Some railways, primarily in the northeast, used standard gauge of 4 ft 8+1⁄2 in (1,435 mm); others used gauges ranging from 2 ft (610 mm) to 6 ft (1,829 mm). As a general rule, southern railroads were built to one or another broad gauge, mostly 5 ft (1,524 mm), while northern railroads that were not standard-gauge tended to be narrow-gauge. The Pacific Railroad Acts of 1863 specified standard gauge.^[1]

Notable exceptions were the 6 ft (1,829 mm) railroads that predominated in the first part of the 19th century in New York State, and the 5 ft 6 in (1,676 mm) lines centered on Portland, Maine. Problems began as soon as lines began to meet, and standard gauge was adopted in much of the northeastern U.S. Standard gauge had spread widely across the country by the late 19th century except in some parts of the South; it was adopted there in a two-day changeover on May 31-June 1, 1886.

Today, standard gauge is used almost everywhere in the U.S. Non-standard gauges remain in use only for some municipal and regional mass transit systems not requiring interchange of equipment.