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 Hiawatha Set Die Cast Shell W/whistling Tender O-gaugeHigh Grade Set Lionel Prewar O Gauge Passenger Cars 2600 2601 2602 (dakotapaul)Prewar American Flyer O Gauge Up Streamliner Passenger Set 1632 1636 1636 1636Pre War Lionel? American Flyer? O Gauge Locomotive Train Good Condition 13Marx O Scale / Gauge New York Central 333 Meteor Passenger Train SetLionel #736 Lts Berkshire Loco & Tender W/original Master Carton O-gauge No ResLionel No. 6-29191 Milwaukee Road Hiawatha 4-car Aluminum Set O Gauge - Bargain!Af O Gauge Prewar American Flyer Lines Steam Locomotive & Tenders (2)1prewar Lionel O Gauge 253e Locomotive 607 608 Train Car Observation Set VintageVintage Varney? Brass 0-6-0 Engine "o" Gauge * W/ Custom Case * Needs FinishingLionel & Ives O Gauge Prewar Tinplate Passenger Cars (4)1925 Hornby O Gauge 0-4-0 Lms No. 2710 Locomotive / Tender C/wPostwar Lionel O Gauge No.2345 Wp F-3 Aa Unit Diesel Engine SetOld Lionel Train Santa Fe Engine & Dummy Set 2333 O Gauge Post WarAtlas O 2-rail O-gauge #5 Turnouts, 4 Left, 2 Right Plus Rivarossi Left SwitchBing, New York Central 5 Piece Train Set,o Gauge,electric Cast Iron Engine, Runs2pre-war Lionel O Gauge 262e Locomotive Tender 610 612 Train Car Observation SetMarx Trains 10391 Nyc 20th Century Pass Set Boxed O-gauge #x8816American Flyer Prewar O Gauge 496 497 Green Passenger CarsLionel 710 Prewar Pullman Car O GaugeLionel Pre-war "o" Gauge #260e Steam Loco & Tender-all Original, Needs Work-niceBing Gauge 1 Baggage CarLionel Trains O Gauge Set 11837 Gp-9 2397 + 6 Diecast Ore Cars & Caboose New3pre-war American Flyer 3046 Locomotive 1201 1203 3046 Train Set Vintage O GaugeMth 3-rail O Gauge Union Pacific 4-12-2 #9010 Item #20-3294-1 Mint!Lionel Fastrack Lot Train Fasttrack Track Straight 10 Inch O Gauge 6-12014 (10)Ry Models O Scale Sacramento Northern Tank Car Brass O Gauge Rare Paint JobIves / Lionel Pre-war Standard Gauge Train Collection - Cars, Accessories, TrackAmerican Flyer 565 Atlantic And 564-c Chugging Tender, O GaugeLionel 2378p Milwaukee Rd F3a Power Unit New Cab Postwar O-gauge #x5989 Brass Pacific Boiler And Cab O Gauge Kit General Model Corp Plus ExtrasStandard Gauge Lionel Lines No. 219 Crane 20 Tons No Reserve AuctionIves O Gauge Clockwork No 25 Locomotive Runs But For Parts Or RestoreAf O Gauge Postwar Accessories (9)Lionel O Gauge # 1666 Steam Locomotive 2-6-2 Williams O Gauge Southern Pacific Non-powered Gp-9 Diesel LocomotiveLot Of Lionel O Gauge Trains Accessories & More-6472, 392,1033, 309,310Bing - O Gauge - Pullman Bogie Coach "minerva" - Spares Or Repair.Lionel Trains Norfolk Southern Gp38 Diesel Locomotive & Lighted Caboose, O GaugeLionel O Gauge # 2253 Santa Fe F-3 Dual Motor Aa Units W/ Magne-traction American Flyer Rubber Roadbed 16 Straight 22 Curved S Gauge Good Cond Bing - O Gauge - Pullman Bogie Coach "cassandra" - Spares Or Repair.Lionel Odyssey O Gauge 4-12-2 Item #6-38029 - Very Nice Condition!Lionel 2378c Milwaukee Rd F3b Non-power Unit New Cab Postwar O-gauge #x5990Lionel 1101, 1654 & 2026 O Gauge Postwar Steam Locomotives (3)62 Sections Of Lionel Super O Gauge Track In Excellent Condition1940's Lionel O Gauge House Car X2454 PennsylvaniaLionel O Gauge Prewar Freight Cars & Tender (9)Lionel 2383 Santa Fe Locomotives O Gauge Not Working Good For Parts Qty 2Lionel 6-31960 The Polar Express O Gauge Train Set Ready To Run Needs Repair1940's Lionel O Gauge 1666 Steam Locomotive With TenderLionel Post War O Gauge #6315-60 Chemical Tank Cars Lot Of 2 With Original BoxesLionel O Gauge No.6-14072 Operating Haunted House With Sounds New In The BoxLionel O Gauge Pennsylvania Torpedo 238e K-4American Flyer Pre War O Gage 561 Engine Runs No Front Or Rear TrucksAmerican Flyer O Gauge 4 Rail Whistle Track 1936-8 Pieces Of Straight Track(3) 1930's Lionel O Gauge (2) 603 Pullman, 604 Observation Lot American Flyer Prewar O Gauge Locomotive Engine 561 Williams O Gauge Conrail Diesel Engine Sd-45 Power A Cab# 3740 No. 9937405 Mth O Gauge Premier Prototype Southern Pacific Passenger Car Shells