The Black Hawk Indian War of 1832 led to the expulsion of the Native Americans who had settlements and burial mounds in the area, and set the stage for the founding of Elgin. Thousands of militiamen and soldiers of Gen. Winfield Scott's army marched through the Fox River valley during the war and accounts of the area's fertile soils and flowing springs soon filtered east.

U-46, the second largest school district in Illinois, serves an area of some 90 square miles (230 km2) in Cook, DuPage and Kane Counties. Almost 40,000 children of school age are in its area. Elgin's two public high schools, Elgin High School and Larkin High School, are home to the Gifted and Talented Academy and the Visual and Performing Arts Academy, respectively

According to the United States Census Bureau, the city has a total area of 25.4 square miles (65.8 km²), of which, 25.0 square miles (64.7 km²) of it is land and 0.4 square miles (1.0 km²) of it (1.54%) is water.