[5] What it meant to him is not clear,[6] but various claims have been put forward, including: By 1840 Meehan's 'Dy' had become the single word 'Deewhy', but was split into its present form during the 1920s.

[8] The first land in the area to be listed by the New South Wales government Gazette was 700 acres (280 ha) granted to William Cossar in the early 19th century, James Wheeler purchased 90 acres in 1842, but by the mid-19th century most of the land in what is now Dee Why had been acquired by James Jenkins and other members of the Jenkins family.

Elizabeth Jenkins, eldest daughter of James, gave all her land to the Salvation Army upon her death in 1900, in recognition of their support in her old age.

Access to the beach was limited by the Salvation Army's land, with a wire netting barrier running along its length.

In 1911 it was decided that the tram line that had expanded in sections from Manly since 1903 was to be extended from Brookvale on to Collaroy Beach via Pittwater Road, and soon after to Narrabeen.

[10] From the end of 1938, the trams, as a result of losses due to low population density and competition with new bus routes that duplicated their services, operated only at peak hours for commuters and on weekends for tourists, and finally ceased operating with the final run on 30 September 1939.

[9] In 1971, work began on a new Dee Why civic centre, inspired by Sulman Prize-winning architects Edwards, Madigan & Torzillo.

The reserve is contained by a seawall running for approximately 400m, and was upgraded in 2006, with new pathways, stairs, lookout platforms, an upper promenade and the restoration of the war memorial.

The rest of the reserve is primarily swamp-based bushland, as well as the coastal dune ecosystem between the lagoon and the sea.

It is a major scenic feature of the Northern Beaches, situated off Pittwater Road, and accessible from Dee Why Parade and The Strand.

There are currently four shopping centres in Dee Why including: Also on Pittwater Road is the Northern Beaches Council Chambers and the Dee Why branch of Warringah Library, one of four networked branches of the Library including Belrose, Forestville and Warringah Mall.

[22] Public transport in Dee Why primarily runs along Pittwater Road in the form of buses, including the high frequency, limited stops B-Line route from the Sydney CBD to Mona Vale, with the B-Line stop located at the intersection with Howard Avenue.

This stop is also served by two frequent bus routes including the 160X travelling westward to Chatswood via Warringah Road, and the 199 connecting Palm Beach to Manly.

Local services connect southwards to Warringah Mall and to Manly via Freshwater, westwards to Frenchs Forest and northwards to Cromer and Collaroy Plateau.

Notably in 1983 at an exhibition match against Manly Warringah, Dee Why won 2–1 with the winning goal scored by guest player George Best, a former Manchester United and Northern Ireland national football team member.

[25] Dee Why was the home of the Evergreen Tennis & Squash Centre, located at Campbell Avenue until its closure in December 2010.

The current church, constructed in 1957 on the corner of Oaks Avenue and Avon Road, is well known for its modern stained glass artwork, installed over a period of years, including the recent addition of the Missions to Seamen Window in the new chapel, from the old MTS Chapel in The Rocks.

The suburb lies within both the state electorates of Wakehurst and Manly, who are represented respectively by the independent member of parliament and former mayor of The Northern Beaches Council, Michael Regan and Liberal Party member James Griffin, a former Manly Deputy Mayor.