On September 8, 1900, the worst recorded natural disaster ever to strike North America hit Galveston Island when a hurricane, first observed 125 miles northwest of Martinique and strengthened after passing over Cuba, came ashore with little warning because of poor communications and inadequate storm-monitoring equipment. Few of Galveston's 38,000 residents evacuated before the bridges to the mainland fell, and a storm surge reaching fifteen feet in parts of the city contributed to an estimated 6,000 to 8,000 deaths. High winds and high water destroyed one third of the city, including 2,636 houses and 1,500 acres of shoreline, and caused property damage estimated at 20 to 30 million dollars. In the years that followed, Galveston built a six-mile seawall standing seventeen feet above mean low tide and raised the city's grade with sand pumped from the Gulf floor and Offatts Bayou, measures that have helped protect it from disastrous flooding during later storms along the upper Texas coast.