O gauge refers to model train tracks whose rails are 1¼ inches apart. Even though O scale model trains frequently run on O gauge tracks, strictly speaking, the two Os have nothing to do with each other.

The letter "O" is actually a misnomer since the designation was initially conceived to identify trains and tracks that were smaller in size than 1, which had been the standard. Since the only number smaller than 1 is 0, that’s how early O scale trains and O gauge tracks were identified, but the letter O (pronounced “owe”) crept into everyday use among model train buffs and has remained the way to refer to the gauge ever since.

The O gauge was introduced to allow toy manufacturers to sell trains that took up less space than their standard counterparts. These trains were also less expensive for customers. At one point or another, Märklin, Lionel, American Flyer, Dorfan, and Ives all made models trains designed to run on O gauge tracks.

This smaller size took off in the 1930s, when affordability trumped most other concerns thanks to the Depression. It was adopted wholeheartedly by Lionel, which sold two different O gauges for its O scale toy trains. Lionel’s regular O gauge track was the same width as its O-27 gauge track (1 ¼ inch), but the O-27 had a lower profile than regular O, and its thinner rails allowed all but the longest O scale model trains to make tighter turns (a circle of O-27 tracks has a diameter of 27 inches instead of 31).

Some of the most famous and sought-after model trains ran on O gauge tracks. Cars with vista domes for Santa Fe, B&O, and New York Central lines, among others, are considered standards of any self-respecting O gauge collection, even if the car was an East Coast line (tunnels back east were too low for vista domes, so in reality they only ran out west). Pointed observation cars such as the ones for the Empire State Express are also popular, as is a short N5 caboose labeled Pennsylvania or Lehigh Valley.

Other model trains sought by O gauge collectors include a work caboose with a boom tender, a Fairbanks-More Trainmaster locomotive (it was painted orange and blue, even though those colors never appeared in real life), and steam locomotives such as Lionel’s S2 Turbine. After World War II, Lionel actually made four versions of the S2 locomotive in both O and O-27 gauges.


Best of the Web (“Hall of Fame”)

Airfix Model Railways

Airfix Model Railways

Dave McCarthy's Airfix Model Railway treasure trove is an in-depth archive of the company's plastic railway kits fr… [read review or visit site]

Gateway NMRA

Gateway NMRA

This great reference site for model railroaders, from the Gateway (St. Louis) division of the NMRA (National Model … [read review or visit site]

HOseeker.net

HOseeker.net

This site is a treasure trove of HO scale model railroad manufacturer catalogs and other reference information, inv… [read review or visit site]

Postwar Lionel Trains Library

Postwar Lionel Trains Library

Bernie Schulz’s Lionel Trains Library focuses exclusively on postwar Lionel trains and accessories. The site cont… [read review or visit site]

Eric's Trains

Eric's Trains

Eric Siegel's site displays his collection of O-gauge/O-scale trains, tracks, turntables, and other accessories. A … [read review or visit site]

Tech Model Railroad Club of MIT

Tech Model Railroad Club of MIT

MIT's model railroad club, as one might expect, has one of the best websites for learning about how people play wit… [read review or visit site]



Clubs & Associations

Discussion Forums

Other Great Reference Sites

Most watched eBay auctions    

American Flyer Pre-war "o" Gauge Chrome Streamline Cars Set/3-1939-gorgeous!American Flyer Pre-war "o" Gauge #447 "scale" Hudson Locomotive-1939-gorgeous!Ross #4 3-way O Gauge Yard Switch ExWilliams Brass O Gauge No.5450 Nyc Dreyfuss Hudson Steam Engine & TenderAmerican Flyer Pre-war "o" Gauge Hiawatha Set-1937-all Original-Lionel Trains Great Northern Aba F-2 Locomotive Engine Set O Gauge CrewtalkBassett-lowke 2-6-0 Live Steam "mogul", Marklin Hornby Bing O-gauge LionelLionel Postwar 1954-1956 O Gauge 2356 Southern F3 Diesel Locomotive A-b-a SetOriginal Chicago American Flyer O Gauge #9900 Burlington Zephyr Train Set-1930'sLionel O Gauge "the Congressional" W/ 2340 Gg-1, 2341, 2342, 2343 & 2344 & BoxMarklin O Gauge Searchlight Wagon - Army Camouflage FinishLot 228- O Gauge Iron Horse Models Brass Wagon Top ClimaxLot 250-o Gauge Ghb International Custom Brass Brill Model 250 Gas-electric Ver1Lot 249- O Gauge Iron Horse Models Custom Brass Vertical Boiler ClimaxLionel Post-war "o" Gauge #2332 Pennsylvania Gg-1 Electric Model Railroad TrainAtlas 6910 Motorized 24 Inch O Gauge Turntable Ln/boxLionel Prewar Standard Gauge 4 Car Passenger Set 419, 2- 418, 490 NicePrewar Lionel Standard Gauge No.33 Electric EnginePolar Express 6-31960 Lionel O Gauge Train Set Bassett-lowke Lms 1924 Lms Post Office Car, Marklin Hornby Bing O-gauge LionelAtlas Trains 10 Piece 40" Straight Track Lot 6058 O Gauge 3 RailLionel O Gauge No.6-18063 Nyc Commodore Vanderbilt Steam Engine In The BoxLionel Postwar O Gauge Promotional Set 9745 Channel Master 175 243 310 6812 3376Lionel Set "o" Gauge: Post War Illuminated 2530 2531 2532 2533 2534 O/b'sOriginal Postwar Lionel O Gauge Ocs 11 Curve & Oss 45 Straight Track, NosLionel Canadian Pacific F3 Aba Diesel Set 8365/8469/8366 O Gauge TrainsLionel The Milwaukee Road F3 Aba Diesel Set 8555/8575/8557 O Gauge TrainsLionel O Gauge No.6-19060 Nyc 4 Car Pullman Heavyweight Passenger Set New In BoxBassett-lowke Lms 4-6-0 "royal Scot", Marklin Hornby Bing O-gauge LionelBassett-lowke Lms 13210 Lms Dining Car, Marklin Hornby Bing O-gauge LionelAmerican Flyer Train Blue Bird Prewar O Gauge Engine & 2 Car & CabooseLionel 7-11020 Harry Potter's Hogwarts Express O Gauge Train SetLionel Pre War 380 Standard Gauge Strap HeadlightsO Gauge - Gar Graves (3) Rail Track - Lot Of 48 Straight Track Sections Unused!Lionel Corp Tinplate Mth 11-80040 Blue Comet 4 Car Set O Gauge Like N W Box Lionel O Gauge Prewar Three # 2623 Manhattan Pullman CarsLionel Baltimore & Ohio F3 Aba Diesel Set 8363/8468/8364 O Gauge Trains1955 Lionel 6-2338 O Gauge Milwaukee Road Gp7 Diesel Engine Runs & Looks GreatLot 279 - O Gauge Ajin Brass Santa Fe Drover's Car - No BoxLionel Pre-war "o" Gauge 1105 Santa Claus & Mickey Mouse Hand Car-1935-gorgeous!Lionel O Gauge Penn Central Gg-1 Electric Engine 6-8850 Engine W/boxLionel Pre War Standard Gauge Passenger Set 309 310 312Model O Gauge Brass Engine Gp35 In BoxO Gauge Marx Mercury Passenger Set Red Working C-5Lionel "o" Gauge Spirit Of 76 6-1776 Diesel Engine Train Set 13 Pcs In O/boxesLionel Prewar Standard Gauge Coal Train Set 318, 2 - 516, 517Lot 285 - O Gauge Iron Horse Models Brass Ac&f 8,000 Gallon Tank CarPrewar Lionel Standard Gauge No.218 Operating Dump Car With The Original Box Lionel 2322-15 Virginian Diesel Original Boxes O GaugeWilliams Aii Brass Crown Edition Usra 4-6-2 "o" Gauge Louisville & Nashville K-4Lionel O Gauge No.6-18064 Nyc L-3a Mohawk Steam Engine Sealed New In The BoxLionel 249 Prewar O-gauge Engine W/265wt Gunmetal Set & Orig. Boxes~ Nice!Prewar Lionel Standard Gauge No.38 Maroon Electric EngineLot 278 - O Gauge Iron Horse Models Brass Up 40' Harriman Car RpoLionel O And 27 Gauge Pennsylvania F3 B Dummy Unit With Horn 8164 Mib Z24 Lionel "o" Gauge Diesel Gp-9 Locomotive Erie Lackawanna 6-8759 And 6-8760 O/b'sModel Train Lionel No. 2148ws "o" Gage Passenger Set & Much MoreLionel Trains Polar Express Train Set - O GaugeLionel Polar Express #1225 Engine & Tender /3 Cars O Gauge/transformer & TrackMth O Gauge #30-4142-e1 Santa Fe F3 Diesel Engine With Proto 2