Humber, navigable estuary of the Trent and Ouse rivers, c.40 mi (60 km) long and from 1 to 8 mi (1.6–12.9 km) wide, NE England, forming the boundary between between the East Riding of Yorkshire and Hull (N) and North Lincolnshire and North East Lincolnshire (S). Spurn Head, with a lighthouse, is at the mouth of the Humber. The shores are generally low, and shoals obstruct shipping in parts. Encroachment of the sea has destroyed former ports, notably Ravenspur. In early English history the Humber was significant as a means of ingress. Hull and Great Grimsby are chief cities and major fishing ports. The Humber Bridge (4,580 ft/1,396 m), linking Hull with the estuary's southern shore, was opened in July, 1981, and is one of the longest suspension bridges in the world.