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    

Hornby O Gauge - Nos 2 Special Lms Compound 1185 Locomotive & Tender -boxedHornby O Gauge 31801 4-4-2 Clockwork 3c Locomotive & Tender -r/viera (nord)Hornby O Gauge 1932 4-4-2 T E220 20 Volt 3 Rail GwrHornby O Gauge L2471 E320 Flying Scotsman Locomotive 20v Attention Req'd -boxedLionel Std. Gauge # 10e Electric Engine + 332 339 341 Passenger Cars(dakotapaul)Nice Lionel No. 115 Automatic Train Station Prewar O Gauge No Reser (dakotapaul)Lionel 263e Locomotive "o" Gauge Blue Comet ? Pre-war ? No ReserveIves "o" Gauge 3257r "gray Ghost" Passenger Set, Circa 1926, Very Nice-rare! American Flyer Prewar 0 Gauge 1661,1661,1662 &1623 Green Passenger Car SetO Gauge American Flyer Pre-war K-5 4-6-2 Steam Freight Set W/7 Cars Gb EsVintage Hornby O Gauge C 574 No.2 Corridor Coach X 2 In Original Boxes.High Grade Lionel O Gauge Postwar No. 6557 Smoking Caboose +box (dakotapaul)O Gauge -k-line Nyc Empire State Express Steam Engine & Tender Cab # 5426 Gb EsAmerican Flyer Hudson 4-6-4 Locomotive / O Gauge / Loco OnlyVintage Hornby O Gauge Em 320 Lms 2270 Tank Locomotive 20v L2475 In Original BoxPrewar Lionel Standard Gauge No.200 TurntableIves "o" Gauge 131 Tin Lithographed Baggage Car, Circa 1910, All Original-nice!Lionel O Gauge 6-11711 Santa Fe F-3 A-b-a- Diesel Set In BoxVintage Hornby O Gauge Te 511 No.2 Special Tender Southern 850 In Original Box.Prewar Lionel Standard Gauge No.380 Electric EnginePostwar Lionel O Gauge No.681 Turbine 6-8-6 Steam Engine & 2671w Whistle TenderLionel 0/027 Gauge Red Wood Valley Express Old Time Steam Engine Train Set Marx Army Flatcar W/ Operating Tank # 572st * O Gauge Military CarLionel Harry Potter Hogwarts Steam Engine Locomotive Train O Gauge 7-11020-eHornby 0 Gauge/ Dinky Station Hoardings - Set Of 4 In Box - MintJanuary 1989 Overland Ajin Brass O-gauge 2-rail Dash 8 LocomotiveMth Premier O Gauge Csx Es44ac Locomotive Non PoweredLionel Alaskan 0-027 Gauge 27"x 63" Oval Track Complete Diesel Train Set 6-11972Prewar Lionel Standard Gauge No.220 Floodlight CarIves 1100 O-gauge Electric Train Set Circa 1916-17Lionel O Gauge 675 Engine W/ 2466wx, 2443, 2442 (2) Cars 5pc As Shown Lionel O Gauge # 746 Norfolk & Western 4-8-4 Steam Loco, # 746w Tender & BoxesIves O Gauge No.5 Windup Locomotive No.1 Tender No.50 Baggage & Lionel 801 Cabo Postwar Lionel O Gauge # 736 Berkshire 2-8-4 Steam Engine & 2046w Whistle TenderLionel 2056 Locomotive Steam Engine In Box 027 GaugeK-line K-1112 Hershey's Chocolates Train Set O And O27 GaugeLionel 6-8480 Union Pacific F3-a Powered And Dummy Units O Gauge RailroadVintage Hornby O Gauge Pullman Coaches In Need Of RestorationLionel O Gauge No.6-18023 Western Maryland Shay Steam Engine With BoxLionel O Gauge Train Engine #736K-line K2436-2002 Metrolink F59phi Railsounds-tmcc Equipped O-gauge Lobaugh Brass 'o' Gauge Heinz Pickle Tank Car KitLionel O Gauge Blue Comet Steam Locomotive And Tender In Ob 6-8801Lionel Post War O Gauge 2243p & 2243c Santa Fe F3 Diesel Locomotive Engine BoxedSet Of Three Original Pre-war Lionel 0/027 Gauge Tinplate Passenger CarsO Gauge Marx Train Steam Engine Train Set # 10271 Coal City Flyer Set Gb EsLionel O Gauge Prewar 260 Loco W/ 263w Tender ProjectVintage Lionel Gg-1 Penn Central 8850 O & 027 Gauge Engine Clean In Box Williams Crown Edition O Gauge Santa Fe 4 Car Metal Passenger Set For LionelLionel Zw 275 Watt Transformer 1950’s Postwar O-gauge TrainPrewar Lionel O Gauge Peacock Passenger Car Set 607 & 607 & 608Postwar Lionel O Gauge No.2338 Milwaukee Road Gp-7 Diesel EngineLionel Pre-war O Gauge #252 Electric Train EngineLionel O Gauge Train Engine #726Lionel O-gauge 6-18001 Rock Island R.r 4-8-4 Northern Diecast Locomotive New MibNew Williams 562 Rio Grande Locomotive Engine Fm509 O-gauge Electric Model TrainMth 11-6022-0 O Gauge 262e Traditional Steam Engine (black W/brass Trim) Ln/boxWeaver B&o Emd E-8 Aa Both Powered Diesel Engine Set, O Gauge 3-rail Mib NewAmerican Flyer Lines Locomotive & Tender 4 Cars Complete Train Set Wide GaugeDorfan O Gauge 8-wheel 610 Crane Or Derrick Car