Aurora (ərôrˈə, ô–) [key]. 1 City (1990 pop. 222,103), Adams and Arapahoe counties, N central Colo., a growing suburb on the east side of Denver; inc. 1903. Founded during the silver boom of the 1890s, it is now a business and technical center and Colorado's third largest city. Manufactures includes furniture, aircraft fittings, electrical equipment, precision measurement instruments, magnesium products, computer software, and paper. Tourism and construction are also important. The former Fitzsimmons Army Medical Center is being converted to business and research use. 2 City (1990 pop. 99,581), Kane co., NE Ill., on the Fox River; inc. 1837. It has large railroad yards and a variety of manufactures, including paper and plastic products, rods and bearings, controls (thermostats), foods, and consumer goods. It was one of the first cities to use electricity for street lighting (1881). It is the seat of Aurora Univ. and of a notable historical museum. A riverboat casino opened in the city in 1993.