Until recently there were 49 elected members, eight Senators, 12 Constables and 29 Deputies. In 2022 the office of Senator was discontinued and the election returned only Deputies and Constables to the States.
The States Assembly originated at an unknown time, before 1524. It developed as an offshoot of the Royal Court, the assembly of the Bailiff and Jurats which had previously been responsible for all aspects of island administration, including the creation of new legislation and the administration of justice. At some point, probably in the early 16th century, the Constables and Rectors of the 12 parishes were co-opted to advise the Court and eventually the assembly of Bailiff, 12 Jurats, 12 Rectors and 12 Jurats became known as the States of Jersey
Of these, the Rectors were appointed for life, the Jurats, initally appointed but subsequently elected by property owners, also for life; and the Constables were elected for three-year terms. In the 19th century it was accepted that the States, which by then functioned entirely apart from the Court, with the exception that the Bailiff was, as he remains to this day, the president of both assemblies, should have broader representation of the whole population.
Fourteen Deputies, first elected in 1857, were added to the Assembly. In 1907 a law was passed to increase the number of Deputies in St Helier to six. The composition then remained unchanged until the Second World War. After the War a major review of the island's government was undertaken and the Jurats and Rectors ceased to be States Members, being replaced by 12 Senators, elected on an all-island franchise to serve for nine years (subsequently reduced to six), and an additional 14 Deputies, representing constituencies which were either whole parishes or divisions of the larger parishes.
In 1974 the number of deputies was increased to 29: St Ouen, St Peter, St John, St Mary, Trinity, St Martin and Grouville have one Deputy each, St Lawrence and St Clement two each, St Brelade three in two districts, St Saviour five in three districts, and St Helier ten in three districts.
In 2011 the number of Senators was reduced to 8.
The Bailiff, or his Deputy, is the president, or speaker of the assembly and the Dean and Attorney-General both have the right to attend and speak, but not to vote.