In 1905 , 110 acres owned by William A. Clark , on which he built a railroad to Southern California were auctioned and Las Vegas was founded as a railroad town . Las Vegas officially became a city in 1911 . Las Vegas was established as a railroad town on May 15 , 1905 , when 110 acres ( 44.5 ha ) owned by the San Pedro , Los Angeles and Salt Lake Railroad , was auctioned off in what is now downtown Las Vegas .