In 1831, the Baltimore and Ohio Railroad (B&O) received approval of a plan to build its Washington Branch. Passenger train service between Baltimore and Washington began in 1835. As part of the construction, the railroad company built its last roundhouse (the current Amtrak yard) one mile outside the city limit. The railroad then worked with land speculators to develop the tract immediately next to the roundhouse as "Ivy City". Ivy City became an early Washington suburb. It housed railroad employees and give a formal mailing address to the roundhouse.