What was the type of the first Boston transportation system in US?

Answer 1

The first attempts to have public transportation were by horse-drawn stagecoaches, as far back as 1793. Eventually, cities moved away from horse-drawn vehicles, and when electrification came along in 1889, Boston had street-cars and trolley cars, which traveled above-ground. In the 1890s, there were also elevated railways. But you may be referring to the subway (called the "underground" in countries like England). Boston had the first subway system, trains that ran beneath the city, in underground tunnels. The subway opened for business in July 1897, and while most of the stations have been updated and the tracks modernized, the subway system is still in use today.