Question: One of Adelaide's high streets is named after which British monarch who was the third son of George III and died within a month of the street naming?

Context paragraphs:
Victoria Square, Adelaide: Victoria Square, also known as Tarntanyangga or Tarndanyangga , is a public square in the South Australian capital of Adelaide.  The area was named "Victoria Square" by the Street Naming Committee on 23 May 1837, after Princess Victoria, then heir presumptive of the British throne.  Less than a month later the King died and Victoria became Queen.  The Kaurna people know the area as Tarndanyangga, "The Dreaming Place of the Red Kangaroo".  In line with the Adelaide City Council's recognition of Kaurna country, the area is officially referred to as Victoria Square/Tarndanyangga.  The square was upgraded in 2014, new lighting was added and the fountain was moved from the northern end to the southern tip of the square.  During the Christmas period, it is traditional for a 24.5 m high Christmas tree to be erected in the northern part of the square.

Street Naming Committee (Adelaide): The Street Naming Committee was set up to decide the names of the streets, the squares and the river of the new settlement of Adelaide, South Australia, as it had been laid out by Colonel William Light in 1837.  Light's map corresponds to the modern Adelaide city centre and North Adelaide.  The committee met on 23 May 1837.

Chrisom: Anciently, a chrisom, or "chrisom-cloth," was the face-cloth, or piece of linen laid over a child's head when he or she was baptised or christened.  Originally, the purpose of the chrisom-cloth was to keep the "chrism", a consecrated oil, from accidentally rubbing off.  With time, the word's meaning changed, to that of a white mantle thrown over the whole infant at the time of baptism.  The term has come to refer to a child who died within a month after its baptism—so called for the chrisom cloth that was used as a shroud for it.  Additionally, in London's Bills of Mortality, the term chrisom was used to refer to infants who died within a month after being born.

King William Street, Adelaide: King William Street is the part of a major arterial road that traverses the CBD and centre of Adelaide (the capital of South Australia).  It was named by the Street Naming Committee on 23 May 1837 after King William IV, the then reigning monarch, who died within a month.  King William Street is approximately 40 m wide, and is the widest main street of all the Australian State capital cities, which are significantly narrower by comparison.  It is historically considered one of Adelaide's high streets, for its focal point of businesses, shops and other prominent establishments.

Whitmore Square: Whitmore Square is a public square in the centre of the south-western quarter of the Adelaide city centre.  It surrounds the intersection of Sturt and Morphett Streets.  It was named by the Street Naming Committee after William Wolryche Whitmore, a British Member of Parliament who introduced the South Australia Foundation Act to the British House of Commons.  It is also known as "Ivaritji", a Kaurna name meaning "gentle, misty rain."  Ivaritji (1847? -1929), also known as Amelia Taylor, was the (then) last remaining speaker of the Kaurna language.

George III of the United Kingdom: George III (George William Frederick; 4 June 1738 – 29 January 1820) was King of Great Britain and Ireland from 25 October 1760 until the union of the two countries on 1 January 1801, after which he was King of the United Kingdom of Great Britain and Ireland until his death.  He was concurrently Duke and prince-elector of Brunswick-Lüneburg ("Hanover") in the Holy Roman Empire until his promotion to King of Hanover on 12 October 1814.  He was the third British monarch of the House of Hanover, but unlike his two predecessors, he was born in Britain, spoke English as his first language, and never visited Hanover.

William IV of the United Kingdom: William IV (William Henry; 21 August 1765 – 20 June 1837) was King of the United Kingdom of Great Britain and Ireland and King of Hanover from 26 June 1830 until his death.  The third son of George III and younger brother and successor to George IV, he was the last king and penultimate monarch of Britain's House of Hanover.

List of British monarchy records: The longest reign of a British monarch is that of the current monarch, Elizabeth II ( since 6 February 1952).  The second longest reign is the 63 years 216 days of Victoria between 1837 and 1901.  Queen Elizabeth II's reign became longer than Queen Victoria's on 9 September 2015.  The third longest reign was that of George III, who reigned for 59 years 96 days between 1760 and 1820.

Hindmarsh Square: Hindmarsh Square is a public square in Adelaide, South Australia.  It is located in the centre of the north-eastern quarter of the city, and surrounds the intersection of Grenfell and Pulteney Streets, near the eastern end of the Rundle Mall.  Pirie Street forms the southern boundary of the square.  It was named by the Street Naming Committee after John Hindmarsh, the first Governor of South Australia.

P Street (Washington, D.C.): P Street refers to four different streets within the city of Washington, D.C. The streets were named by President George Washington in 1791 as part of a general street naming program, in which east-west running streets were named alphabetically and north-south running streets numerically.

Supporting paragraphs: King William Street, Adelaide William IV of the United Kingdom
Answer: King William IV