Before being renamed in 1918, the mountain had been called Green Mountain. The new name honors the French explorer and adventurer Antoine Laumet de La Mothe, sieur de Cadillac.
From 1883 until 1893 the Green Mountain Cog Railway ran to the summit to take visitors to the Green Mountain Hotel on the summit. The hotel was burned down in 1895. Also in 1895, the cog train was sold and moved to the Mount Washington Cog Railway in New Hampshire. https://en.wikipedia.org/wiki/Cadillac_Mountain]