Question: Who invented the steam engine in the 1800s?
Disambiguated questions and answers: question: Who invented the first full-scale steam steam engine inside a working railway locomotive in the 1800s?
Who invented the horizontal steam engine in the 1800s?
Who invented the high pressure steam engine in the US independently of Trevithick?
answer: Richard Trevithick
Trevithick
George Henry Corliss
Oliver Evans
Natural Questions answer: James Watt (from the Wikipedia article "Steam engine")