Which Las Vegas? There is no Amtrak train to Las Vegas, NV. The two Amtrak stations here are for buses only. However, there is a station in Las Vegas, NM. It's on 500 Railroad Ave @ Lincoln.

Amtrak Tru Way Bus Station in Las Vegas, NV
1-800-872-7245

Amtrak Train Station in Las Vegas, NM
(800) 872-7245‎