It is a typical Lake District "ribbon lake", formed after the last ice age by a glacier scooping out the valley floor, which then filled with meltwater. Ullswater was formed by three glaciers. Surrounding hills give it the shape of an extenuated "Z" with three segments or reaches winding through them. For much of its length, Ullswater formed the border between the historic counties of Cumberland and Westmorland.
The origin of the name Ullswater is uncertain. Whaley suggests "Ulf's lake", from Old Norse personal name Ulfr plus Middle English water, influenced in usage by the Old Norse vatn (water or lake). Ulfr is also the Old Norse noun meaning wolf, and Hutchinson thought that the name might refer to the lake as a resort of wolves, or to its elbow-shaped bend (citing a Celtic ulle)."
Some say it comes from the name of a Nordic chief named Ulf, who ruled over the area. There was also a Saxon Lord of Greystoke called Ulphus, whose land bordered the lake. The lake may have been named Ulf's Water in honour of either of these, or after the Norse god Ullr. Hodgson Hill, an earthwork on the north-east shoreline of Ullswater may be the remains of a Viking fortified settlement.
"Superficial inspection suggests a similarity between Hodgson Hill and other known Viking shore settlements in England (Julian D. Richards, Viking Age England, London: Batsford and English Heritage, 1991, pp. 22-3). It would have been in an ideal strategic position, guarding water and shoreline east-west routes at the eastern fringe of the Viking colony stretching from St Bees through Crosthwaite into the Cumberland dales. The earthworks would possibly have timber ramparts for additional defence. Around one or two hundred armed Vikings could be accommodated within. The Hodgson Hill site suggests a possible slipway at its western extremity for the beaching of boats. These boats would have been used to establish military dominance of the entire Ullswater area." - The Hodgson Clan Website (hodgson-clan.net)
The lake has been a tourist destination since the mid-18th century. By the 1890s, Ullswater had become a fashionable holiday destination for the British aristocracy, thanks to its good sailing conditions and proximity to fell shooting estates. In 1912, Wilhelm II, German Emperor visited Ullswater and toured the lake on the MY Raven, which was re-fitted to act as a royal yacht. A shooting lodge (The Bungalow) was constructed for the Kaiser at Martindale by the major local landowner, Hugh Lowther, 5th Earl of Lonsdale.
Ullswater's attractions include the Ullswater "Steamers" which offer trips around the lake calling at Pooley Bridge, Glenridding, Howtown and Aira Force. These sail all the year round and were originally working boats which from the 1850s moved mail, workers and goods to and from the Greenside Mine at Glenridding, which closed in 1962.
Ullswater is also a sailing location with several marinas round the lake. It is home to the Ullswater Yacht Club and the Lord Birkett Memorial Trophy, held annually on the first weekend in July. This regularly attracts over 200 sailing boats for two races covering the length of the lake. There are also facilities for diving, rowing and motorboats. Another of attraction is the waterfall of Aira Force, midway along the lake on the western side. Ullswater lies partly within the National Trust's Ullswater and Aira Force property. Close to the falls is Lyulph's Tower, a pele tower or castellated building built by a former Duke of Norfolk as a shooting box. The Sharrow Bay Country House hotel stands on the lake's eastern shore.