A live steam machine or device is one powered by steam, but the term is usually reserved for those that are replicas, scale models, toys, or otherwise used for heritage, museum, entertainment, or recreational purposes. Revenue-earning steam-powered machines such as mainline and narrow gauge steam locomotives, steamships, and power-generating steam turbines are not normally referred to as "live steam".
The term live steam usually refers to a model steam locomotive, or any other steam-operated model that is powered by steam produced by boiling water. Steam rollers and traction engines are popular, in 1:4 or 1:3 scale, as are model stationary steam engines, ranging from pocket-size to 1:2 scale.
Ridable, large-scale live steam railroading on a backyard railroad is a popular aspect of the live steam hobby, but it is time-consuming to build a locomotive from scratch and it can be costly to purchase one already built. Garden railways, in smaller scales (that cannot pull a "live" person nor be ridden on), offer the benefits of real steam engines (and at lower cost and in less space), but do not provide the same experience as operating one's own locomotive in the larger scales and riding on (or behind) it, while doing so.
One of the most famous live steam railroads was Walt Disney's Carolwood Pacific Railroad around his California home; it later inspired Mr. Disney to surround his planned Disneyland amusement park with a working, narrow gauge railroad.
The live steam hobby is especially popular in the UK, USA, and Australia. All over the world, there are hundreds of clubs and associations as well as many thousands of private backyard railroads. The world's largest live steam layout, with over 25 miles (40 km) of 7-1/2" trackage is Train Mountain in Chiloquin, Oregon, USA. Another notable layout is the one operated by Los Angeles Live Steamers or the Riverside Live Steamers.
Often the gauge has little to do with the scale of a locomotive since larger equipment can be built in a narrow gauge railway configuration.
There are several common fuels used to boil water in live steam models, depending on their scale:
A live steam festival (often called a "Steam Fair" in the UK and a live steam "meet" in the USA) is a gathering of people interested in steam technology. Locomotives, trains, traction engines, steam rollers and tractors, steam boats and cars, and stationary steam engines may be on display, both full-sized and in miniature. Rides may also be offered.
"Live Steam" is a U.S. magazine, founded in 1966 and devoted to the live steam hobby, as well as to other uses of miniature and full-size steam. Originally, it was a mimeographed newsletter, but soon expanded into magazine format. In 2005, the name was changed to Live Steam & Outdoor Railroading. It is currently published bi-monthly, in full color, with a press run of slightly over 10,000 (Dec. 2004).