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 9900 Prewar Burlington Zephyr Tinplate 5-car Set O-gauge *rare*Lionel # 773 "o" Gauge Hudson Steam Loco 1950 W/ 2426w Ln/ob Great! (dakotapaul)3 Ives O Gauge Trains 129 Saratoga 130 Buffet 131 U.s. MailAmerican Flyer Prewar O Gauge Scarce Streamliner -minihaha-nrHornby O Gauge No.2 Station With Fenced Ramps - Windsor - 1930's TinplateAmerican Flyer Pre-war 3 Car Passenger Set 3380 3381 3382 O-gaugeIves 3238 Late Cast Iron Loco + 129 Saratoga & 130 Buffet Passenger Cars 0 GaugeAmerican Flyer 3210 Tinplate Green Tank Car Prewar O-gaugeLionel Trains 1920 Prewar Standard Gauge Tunnel For Engine Cars Huge Original UsVintage Hornby Meccano O Gauge Maroon Nord 31801 Clockwork Locomotive - Ib F08Rare Wide Gauge Mail Baggage Set W/box #4122 American Flyer Standard Toy TrainAmerican Flyer O Gauge The Royal Blue.556 Loco.tender&pass.cars.htf.& Boxs.Prewar Lionel Standard Gauge No.217 Orange & Maroon Caboose With Original BoxLionel 6-35454 Amtrak Amfleet Cab Controlled End Passenger Car O Gauge Train6 Ives O Gauge Trains 63 Nyc & Hr Gravel 67 Caboose Lumber 65 LivestockVintage Hornby Meccano O Gauge Maroon Nord 31801 Tender Coal Train - Hk F08Lionel Santa Fe Locomotive A & Dummy B 2343 Gm Train No Reserve O GaugeVintage Hornby Meccano O Gauge Riviera Blue Sleeping Car Passenger Coach- Qa F08Lionel Fastrack Lot Train Fasttrack Track Straight 10 Inch O Gauge 6-12014 (10)Lionel Lines Locomotive & Tender No.260e-used-o GaugeLionel O Gauge #681 Engine With 2671w TenderO Gauge Caterpillar Train Set Freight Ready To Run Rail King 3040531 Nice Set!!Lionel Lines Super Motor No. 8 Prewar Standard Gauge Engine Locomotive TrainsBowman O Gauge Gwr 1st 3rd Class Passenger Coach 10152 Model 550 Boxed VintageEts Vintage O Gauge Scale 1:45 Electric Railway Tinplate Train Set No Reserve!!!Williams O Gauge #20197 F 2 A A Texas Special Powered & Dummy DieselsLionel Prewar 134 Automatic City Train Station - Bright Paint - O Gauge NrRare Vintage 82 Ft. Pullman Lounge Observation Car * "o" Gauge * Needs FinishingLionel /ross O Gauge Track And SwitchesPostwar Lionel O Gauge Hudson Type Steam Engine Locomotive No. 2046 & Box | RsLionel Big "o" Gauge 4-4-0 The General Steam Locomotive & Tender With Other CarsPrewar "0" Gauge American Flyer Steam Loco & Tender # 545 C-2K-line Aluminum O Gauge Prr 4 Car Streamlined Passenger Car Set In The BoxCustom Trains O Gauge No.sa-1005 No.2331 Virginian Fm Trainmaster Diesel EngineVintage Hornby Meccano O Gauge United Dairies Milk Tank Freight Wagon - Je F08Set Of 3 Postwar Lionel O Gauge No.2532 Aluminum Silver Range Vista Dome CarsAntique Lionel Lines 752e, 753 & 754 Union Pacific Model Trains (o-gauge) SilverLionel Trains Rare Dark Grey, O & O-27 Gauge Operating Coal Dumping Ramp Set 456Postwar Lionel O Gauge No.646 4-6-4 Steam Engine & No.2046w Whistle TenderAtlas O Gauge Track120 Pieces Lionel Post War 027 Gauge 3 Rail Track-curves And Straight + ExtrasAmerican Flyer Pre-war Die Cast 3 Car Passenger Set 521 524 524 3/16 O-gaugeBrass Steam Engine & Tender 2-10-4 O Gauge 2 Rail Scale KitLionel Prewar O Gauge Gunmetal Grey Engine 1689 E And Tender BoxWilliams O Gauge #20195 F 2 A A Santa Fe Powered & Dummy DieselsAmerican Flyer Lines 3020-used- O-gaugePostwar Lionel O Gauge No.2025 2-6-4 Steam Engine & No.6466w Whistle TenderEts O Gauge Scale 1:45 Electric Railway Tinplate Train Set With Wooden BoxAntique Lionel Trains No. 263w Whistle Tender Car (o-scale Gauge)+ No. 816 BoxLionel O Gauge No.8702 Southern Crescent 4-6-4 Steam Engine & Tender In The BoxVintage Hornby Meccano O Gauge Great Western Guard Brake Van Boxed - Hc F08Bing Cast Iron Wind Up O Gauge Set. O Gauge One Pair Mth Realtrax Real Trax Remote Control Switches Turnouts W/lampsLionel Pre War 258, 257t O-gauge Locomotive & TenderLionel 027 Gauge #221 Gray Dreyfuss Nyc Loco/tender 1946K-line Sante Fe Aba Engines And 6 Passenger Cars O GaugeLionel Lines Super Motor Prewar Standard Gauge No.10 Engine/locomotive Vintage Circus O-gauge Lot Of Wood Model Kits Wardie-jay, Big Top Wagons TentAmerican Flyer Pre-war 4 Car Passenger Set 1621g X3 1622g X1 O-gaugeLionel #250 Center Cab Electric O Gauge Set.