The Cadillac was an American automobile manufacturing company established on Earth at the turn of the 20th century.
In the hotel re-creation from the novel Hotel Royale, one of the guests, who went by Texas informed Data that he drove a 1991 Cadillac with 80,000 miles on it from Lubbock, Texas, to the Hotel Royale, located in Las Vegas. (TNG: "The Royale")