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    

Lionel O-gauge Hudson #773 Locomotive 4-6-4 & #2646 Tender 1950's Era Gb Dh9Ives 1122, 4-4-2, Black Deluxe Steam Locomotive, "o" Gauge,1929-1930Prewar American Flyer O Gauge No.531 Nyc Hudson 4-6-4 Steam Engine & TenderPrewar American Flyer O Gauge Cast Aluminum Burlington Zephyr Streamliner Set0 Gauge Mth #20-3029-1 Southern Pacific 4-8-4 Gs 4 Steam Locomotive Gb Dh9O Gauge Mth Santa Fe 2-10-4 Texas Steam Engine W/protosound Gb Dh9Prewar Lionel O Gauge Gray & Red Passenger Car Set 600 & 601 & 602O Gauge Mth #20-3025-1 Southern Pacific 4-8-8-2 Ac-6 Steam Locomotive Gb Dh9Lot (3) Lionel Prewar Tin Plate O Gauge Passenger Cars 1690 & 1691 (dakotapaul)Lionel O Gauge # 736 Steam Locomotive For Parts DnrVintage Hornby Meccano E2e 0 Gauge Engine Shed Tinplate NrO Gauge Mth #20-2185-1 Union Pacific Veranda Turbine Diesel Locomotive Gb Dh9Lionel Postwar O Gauge Set # 2237ws W/ 665 6026w ++set Box No Res (dakotapaul)American Flyer Am Fly O-gauge 429 - 431 Die Cast 0-6-0 SwitcherAmerican Flyer O Gauge No. 1681 2-6-2 Hudson W/ Tender & Original TrackWilliams Brass O Gauge No.3958 Up 4-6-6-4 Challenger Steam Engine & TenderLionel New York Central Hudson 700e 5340 Steam Engine 4-6-4 Full O Gauge In BoxMarklin I Gauge 10000k Crane Car Early 1906 Lionel Post War 726-86 Engine & 2046 W Whistle Tender In Original Boxes O GaugeRich Yoder Brass O Gauge Western Maryland HopperEarly Lionel Prewar O Gauge Passenger Set # 150 Engine 600 Pullmans (dakotapaul)Australian Robilt O Gauge Boxed Train Set Series 101Railking Mth O Gauge Item #30-2162-1 Mta Protosound 4-car Subway Set R-36Lionel Nib - 0-gauge L-3a Mohawk Nyc 4-8-4 Locomotive & Tender #6-18064 Gb Dh9Lionel O-gauge Baltimore & Ohio B&o F3 Aba Set 8363, 8364 8468-1973-75 Gb Dh9Lionel Prewar O Gauge 256 Locomotive Dual Motor Engine Estate FindAmerican Flyer Am Fly O-gauge 429 - 431 Die Cast TenderMarklin I Gauge Acid Car Fantastic ConditionLionel Pre War 752 Up M100000 O Gauge 3 Car Set W 752e, 753 & 754 Runs Well AlLot #1: Williams O-gage Amtrak Fp-45 A-a UnitsLionel Trains Prewar O Gauge 258 With 257t Tender Nice Pair No Damage Runs Good!Railking Mth O Gauge Item #30-2162-1 Mta Protosound 4-car Subway SetMth Full O Gauge Union Pacific Big Boy In Box 3021lp Huge!Lionel Post War O Gauge #736 Engine & #2046w Whistle TenderO Gauge Atlas Seaboard Gp-7 Diesel LocomotiveNos! Lionel 6-19107 19113 19121 19128 19110 O Gauge Santa Fe Toy Train Set 5Lionel O Gauge 6544 Missile Firing Car W/ Seven 7 Missiles Lionel Classics O Gauge 51004 Blue Comet Pass. Set Lionel O Gauge 2037 Engine Set W/ 234w, 6017, 6816, 3419,6448,6424 + AccessoriesMarklin O Gauge Reingold Car With Interior And FiguresLot #3: 9 Car O-27 Gage Assortment With Cannon Box CarNos! Lionel 6-7204 9593 9590 9591 9593 O Gauge Southern Pacific Toy Train Set 1Lionel No.6-12948 O Gauge No.313 Operating Bascule Bridge In The BoxMarklin O Gauge New York Central Ls&ms 2929 Hopper Car Early Lionel # 2343c Santa Fe F3 Diesel B-unit * O Gauge EnginePrewar Lionel O Gauge No.225e Steam Engine & 2235w Die-cast Whistle TenderNew In Box K-line Hershey's Chocolate Products 6-unit O-gauge Train Set Ives Cast Iron Wind Up O Gauge Engine/locomotive #21 Vintage Antique TrainNew In Box Lionel James Gang O27 Gauge 5 Pc.train Set Santa Fe Steam Engine 1981Lionel Prewar Standard Gauge Sunoco Tank Car #215 O27 Gauge Complete Lionel Golden State Arrow Set - 6-1388 With Box Never OpenedNos! Lionel 6-25003 17655 17380 17278 27612 O Gauge Southern Pacific Toy Train13Lionel 6464-250 Western Pacific Boxcar Rare 1966 Only W/original Box O-gaugeLionel O Gauge Postwar No. 2530 Aluminum Baggage Car W/original BoxLionel 1965 "o" Gauge 6 - Unit Diesel Freight Set With Magne - TractionLionel Post-war #665 "o" Gauge 4-6-4 LocoLionel O Gauge 3820 Usmc Flat Car W/ Navy Submarine Train CarLionel #022 1 Pair O-gauge Switch Track W/remotes, Lanterns Voltage Pins WorkingNos! Lionel 6-9589 9592 9591 9590 O Gauge Southern Pacific Toy Train Set 2Lionel Boy Scout Steam Engine Locomotive O Gauge Train Of America Bsa 6-30161-e