Mark IV Monorail

The Mark IV Monorail was the original monorail train model used on the Walt Disney World Monorail System, as well as the Las Vegas Monorail. It went into service on October 1, 1971. The ten trains were designed by Bob Gurr built by Martin Marietta of Bethesda, Maryland. The Mark IV trains were completely replaced by the Mark VI fleet by 1991. The Mark IV was the first "Learjet"-style monorail of the Disney monorails, later followed by the Mark V and Mark VI.

Trains
The Mark IV trains originally consisted of five cars per train, not unlike the then-current 1969 Mark III trains running on the Disneyland Monorail System. Sixth cars were later added. The ten trains were identified by the color of the stripe on their sides:
 * Red
 * Orange
 * Yellow
 * Lime
 * Blue
 * Purple
 * Coral
 * Gold
 * Silver
 * Black

MGM Grand-Bally's Monorail
When the Las Vegas Monorail first opened, it was a free transportation system between the MGM Grand Las Vegas and Bally's Las Vegas, then known as the MGM Grand-Bally's Monorail. The MGM Grand-Bally's Monorail utilized two Mark IV monorails purchased from Walt Disney World for $3.5 million each: Coral and Lime. When the system was extended as the Las Vegas Monorail in 2004, the Mark IV trains were retired in favor of a fleet of new Mark IV trains from Bombardier. These Mark VI trains, however, are different in physical appearance, are shorter, and are completely automated.