The discovery of oil just south of the city in 1914, and north in 1947 fueled a growth that turned the once purely agricultural community into a metropolis. Many American entrepeneurs brought technology and investment funds needed to get Calgary's petroleum industry started in the early 1900's. However, many of those who came for the money stayed around to enjoy the beauty of the area, and eventually became Canadian citizens. The city has enclosed walkways downtown, which are 15 feet above street level, connecting almost half of the downtown buildings. The allows people to eat, work or shop without having to bundle up during the cold winters.