Because that’s the year the first one “arrived in the USA.”
The locomotive credited for being the first steam engine in America was also a British train, shipped to New York from England in 1829. Though it was not American-built, it was the first such locomotive to operate on American soil. This locomotive was the “Stourbridge Lion,” and it marked the official beginnings of an American industry that would lead to vast advancements in the decades that followed.
Because that’s the year the first one “arrived in the USA.”
(Source: https://pabook.libraries.psu.edu/literary-cultural-heritage-map-pa/feature-articles/how-america-got-its-horses-and-got-moving )
Ohhh Steam machine… slaps hand on head thaaaaank youuuuu!