It is located on the Gulf St Vincent coastline of the Lefevre Peninsula about 14 kilometres (9 mi) from the Adelaide city centre.

In 1851, George Coppin, a prominent publican, theatrical entrepreneur and actor, built a two-storeyed timber hotel on the southern corner of The Esplanade and Blackler Street.

In 1856, an official government signal station was established at the intersection of The Esplanade and Semaphore Road, where officers would record the details of all vessels in Gulf St Vincent.

[8] In 1880, an octagonal brick tower with 2-metre (6 ft 7 in) thick walls was erected in Blackler Street to maintain a water supply when the Jervois Bridge had to be raised for passing ships.

[14] In 1928, a merry-go-round, the largest in Australia, was constructed, driven by an electrical lift motor and gearbox, unlike the predominantly steam-driven machines of the era.

[9] In the mid-1930s, the Great Depression brought a decline to Semaphore, with the tram service being closed down and the functions of the Signal Station and Time Ball Tower being moved to Outer Harbor, while the jetty was shortened due to storm damage, with repairs being considered unaffordable.

Semaphore is primarily a residential suburb, although its seaside location makes it a popular local tourist destination, with numerous restaurants, takeaway food outlets and other tourism-oriented businesses.

It overlooks the Fort Glanville steam train, which operates as a heritage item by the National Railway Museum.

[15] The birthplace of Sir Ross Smith, the aviator who flew from the United Kingdom to Australia is preserved to this day[9] at 36 Newman Street.

The Odeon Star in Semaphore Road is the oldest purpose-built cinema in Adelaide, opened on 22 May 1920 as the Wondergraph Picture Palace.

Sandbars extend out a considerable distance, with holes, troughs and channels in the bars creating the major safety hazard on a generally safe beach.

Semaphore Road was voted the People's Choice Award for best main street in South Australia for 2014.

On-road cycling lanes are on most major roads, although operation of these is typically limited to peak hours.