[2] The first HOn30 / HOn2½ ready-to-run (RTR) brand introduced in the US was the AHM MinitrainS,[3] initially manufactured by Egger-Bahn and later by Roco and Mehanoteknika Izola, also known as Mehano.

[7] Other manufacturers to produce HOe in recent years have included Roco, Liliput, Bemo and Tillig.

In 1965 Bob Hayden and Dave Frary stumbled upon an Associated Hobby Manufacturer's AHM[3] "MinitrainS" HOn2+1⁄2 (now named HOn30) train set at a Woolworth's department store and decided to use it to model Maine 2-foot railroads in HO scale.

The product line represented North American prototypes in HO scale, using N-gauge track.

Next came Dave Frary's 12-by-26-foot (3.7 m × 7.9 m) HOn2+1⁄2 Carrabasset & Dead River Ry (C&DR), one of the first known large model railroad to utilize HOn2+1⁄2.

During the mid-1970s a Japanese company, Sango, made a kit for a 2-6-0 Baldwin engine which showed a great improvement in running ability.

From 1978 to 1982, Joe Works, Sango, and Flying Zoo kits and built-up brass models came on the scene.

The following table lists the most popular narrow gauges in HO and OO scale: Model railroaders with layouts and rolling stocks by American standard and usually by British standard use for designation of the scale in English language publications the letter O and not the number 0.

In Great Britain and in the French language it is written sometimes with a hyphen or en dash between the scale and the model gauge, for example, OO–9 or H0-9.