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 5c O Gauge Postwar Service Station Test SetLionel Postwar O Gauge 2032 Erie Alco Diesel Locomotive Set + Brick Master BoxEarly ( C 1911 ) Carette O Gauge 0-4-0 Live Steam Locomotive No 500/35European German Tin Steel Windup O Gauge Train Engine Tender Toy Pre War Williams O Gauge Baltimore & Ohio Aluminum Passenger Cars (5)2 X Pre War Hornby Series O Gauge Rotary Tipping Wagon & Side Tipping WagonAmerican Flyer Pre-war O-gauge 3-car Passenger Set 3381/3381/3382American Flyer Prewar O Gauge Royal Blue 495 494 Passenger Cars Lionel & Ives Prewar Miscellaneous Train Set (engines May Not Run) Gauge OAmerican Flyer S Gauge Steel Railroad Crossing Sign With Bell House (33)Llionel Pre-war #260-e O Gauge Steam Locomotive & Rare 12 Wheel Tender Lionel 'o' Gauge Wabash Trainmaster, 2 Motors, Legacy Equipped, Clean/obLionel Beechcraft Bonanza Transport Car #6500 Plus Original Box O Gauge Lionel Lion Chief Santas Helper Christmas Ready To Run O Gauge Train Set 6-82545O Gauge- Lionel Postwar 2344 New York Central F3 Diesel Aa Loco-lqqk- P196a Vintage Ives Trains O-gauge Electric Engine With Freight CarsK-line O-27 Gauge 5 Die-cast Skeleton Cars With Logs #663-8014 West Sidelc Mint Pair Of Vintage Pre War Dorfan 410 Wide Gauge Train Bridges - Estate FreshHafner O Gauge Overland Flyer Century Of Progress Set W/ Track Switches And BoxK-line Vre F59phi Diesel #v40 K2436-5006 0/0-27 Gauge 182 Piece Lot Of Atlas O Gauge Curve/straight Track (610)Lionel O Gauge Train Set Land's End "it's A Wonderful Life" (limited Edition)Marx O-gauge 3-pc. Up Clockwork Brown & Yellow M10000 Passenger Set 1955 Train "the Milwaukee Road" O Gauge Lionel #2338 Diesel Engine In Box Lionel Pere Marquette Gp38 Engine # 3003 O Gauge Train 6-81028 Diesel 6-81659Williams "o" Gauge #40510 Berkshire 2-8-4 Luxury Lines Steam Engine W/ TenderLionel No. 9519 Preamble Express F-3 Diesel B Unit - Custom Decorated - O GaugeK-line Prsl 15" Interurban Powered & Unpowered Set Of 2 K2780 0/0-27 Gauge Rare Hornby Clockwork Locomotive Lner 460 To Restore Model Railway O Gauge 1124Vintage Postwar Lionel O Gauge No.182-22 Bag Of Steel Blanks - Never UsedLionel Lighted Coaling Tower 6-37912, O Gauge Scale Train Railroad CoalNestle Promotional K-line 6 Unit 0-27 Gauge Train SetLionel 6-30118 Electric Ready To Run O-gauge Christmas Story Train Set In BoxLionel Prr Keystone Lionchief Remote Control Gp38 Diesel 2382 O Gauge 6-82436-eWilliams Milwaukee Road Fm Trainmaster #4126 Orange/black W/horn 0/0-27 GaugeK-line Train Set 0/027 Gauge Vintage Procter & Gamble Diesel Engine Cars Track +Vintage Postwar Lionel No. 6657 D&rg Rio Grande Caboose - O Gauge - NiceK-line 6-22192 Hot Box Operating Bbq Shack - New In Box - O GaugeK-line Electric Trains Diesel Engine 'dual Motor Alco' 0/027 GaugeK-line O Gauge Kennectt Copper Corporation Ore Cars (8) LnFm Wabash Trainmaster No. Sa-1006 0/0-27 Gauge K-line O Gauge Santa Fe Argentine F-3 Aa Diesel Set - No Box - Cab 325 - 326Lionel Paper -- Scarce Prewar Standard Gauge Billboards -- Original!!Lionel O Gauge, 14110 Ferris Wheel Working, Does Not Have Original Box.1970's Marx O Gauge Big Rail Train SetK-line 639106 Yuengling Beer 1992 Limited Edition Tank Car - O Gauge In BoxLionel O-gauge #6-12948 Bascule Bridge 313 Lionel Vintage "o" Gauge Santa Fe, # 2243 Type F3b, 2353 Santa Fe , 2243 Sf F3"o" Gauge North Pole Central - Peppermint Bubbler For Lionel / 3 Rail Trains Lionel 6-1776 Spirit Of '76 U36b Diesel Locomotive Seaboard Scl O Gauge In BoxLionel Celebration Series 760 Va Zw Transformer 18 Volt O-gaugeLionel 18305 Lackawanna Commuter Cars Non-power O-gauge #x3352K-line Union Pacific Mp-15 K2236 Diesel Engine 0/0-27 Gauge NibBrand New K-line K-1401 Hershey's 100th Anniversary Train Set 7 Unit CarsLionel Fastrack O-gauge Curved O36 And 10 Straight Decent AmountLionel Ltd. Edition Norfolk & Western Sd-24 Diesel Engine 6-8266 0/0-27 Gauge K-line Burlington Northern Mp-15 K-2248 Diesel Engine 0/0-27 Gauge NibLionel New York Central Gp-9 Diesel Engine 6-8477 0/0-27 Gauge Lionel Ltd. Edition Canadian Pacific Sd-24 Diesel Engine 6-8152 0/0-27 Gauge Large Lot Of 48 Lionel Ny Prewar O Gauge Track Pieces 16 Straight And 32curved