Cairo ( ) is the southernmost city in Illinois and the county seat of Alexander County. The city is located at the confluence of the Ohio and Mississippi rivers. Fort Defiance, a Civil War camp, was built here in 1862 by Union General Ulysses S. Grant to control strategic access to the rivers, and launch and supply his successful campaigns south. Cairo has the lowest elevation of any location in Illinois and is the only Illinois city to be surrounded by levees. It is in the area of Southern Illinois known as Little Egypt, for which the city is named after Egypt's capital. Several blocks in the town comprise the Cairo Historic District, listed on the National Register of Historic Places (NRHP). The Old Customs House is also on the NRHP. The city is part of the Cape Girardeau–Jackson, MO–IL Metropolitan Statistical Area. Developed as a river port, Cairo was later bypassed by transportation changes away from the large expanse of low-lying land and water, which surrounds Cairo, and due to industrial restructuring, the population peaked at 15,203 in 1920, while in the 2020 census it was 1,733. The entire city was evacuated during the 2011 Mississippi River Floods, after the Ohio River rose higher than the 1937 flood levels, with the possibility of 15 feet of water inundating Cairo. The United States Army Corps of Engineers breached levees in the Mississippi flood zone near Cairo in Missouri to prevent flooding in Cairo and other more populous areas further downstream along both the Ohio and Mississippi rivers. History Beginnings The first municipal charter for Cairo and for the Bank of Cairo were issued in 1818, but without any settlement and without any depositors. A second and successful effort to establish a town was made by the Cairo City and Canal Company in 1836–37, with a large levee built to encircle the site. However, this effort collapsed in 1840, with few settlers remaining. Charles Dickens visited Cairo in 1842, and was unimpressed. The city would serve as his prototype for the nightmare City of Eden in his novel Martin Chuzzlewit. In 1846, 10,000 acres in Cairo were purchased by the trustees of the Cairo City Property Trust, a group of investors including writer John Neal who planned to make it the terminus of the projected Illinois Central Railroad, which finally arrived there in 1855. Cairo had been growing as an important