The square here was created by Sir Charles Barry in the latter half of the 19th century by the clearance of some mean streets and the removal of the accretion of courts and legal offices that cluttered the west side of Westminster Hall. It is populated by the statues of eight eminent politicians and statesmen. Six held office as prime ministers of the united Kingdom. They are -
George Canning (1770-1827), whose statue by Westmacott is on the western perimeter of the square. His administration was for just a few months preceding his death. He was a considerable liberalising influence on several previous administrations, concerning himself with the abolition of slavery and the emancipation of Catholics.
Sir Robert Peel (1788-1850), whose statue is by M. Noble, held office as prime minister from November 1834 to April 1835 and from the election of 1841 to June 1846. He is best remembered for his reorganisation of London's police whereby they gained the title of 'Bobbies'.
Henry John Temple 3rd Viscount Palmerston (1784-1865) has a statue by T. Woolner. His administrations were from 1855 to February 1858 and from June 1859 until his death but he had considerable influence on affairs in Europe as Foreign Secretary in the Whig administrations between 1830 and 1841.
Edward Henry Smith Stanley, 14th Earl of Derby (1799-1869), whose statue is by Matthew Noble, had three brief administration in 1852, 1858-9 and 1866-8 when he handed over to Benjamin Disraeli, 1st Earl of Beaconsfield.
Disraeli also has a statue here which is by Nicolas Raggi. His periods as prime minister (briefly in 1868 and then from 1874 to 1880), were separated by a very effective leadership of the opposition to Gladstone's first administration. In office, his success in diplomatic negotiations with Russia in 1878 earned great praise from Bismarck. He also managed to produce several very successful novels.
A statue of Sir Winston Leonard Spencer Churchill (1874-1965), by Ivor Roberts-Jones, in the centre of the east side of the square presents him in an attitude that makes him appear to be making his way very determinedly to parliament without concern for traffic or any other distraction. His renowned leadership of the United Kingdom, in the Second World War against Germany, was his first period as Prime Minister from May 1940 to July 1945 but as well as being 'in the wilderness' for many years before that he had also held various of the highest offices of state. His second term as Prime Minister was from 1951-55. He also earned his living as a writer.
The statue of Jan Christian Smuts (1870-1950), the South African statesman, is by the sculptor Sir Jacob Epstein (1880-1959) who is probably the most renowned artist whose work is in the square. His subject would probably have been even more renowned had he been made the leader of an Empire wide administration blocking Churchill's arrival in office in 1940 as was, very tentatively, proposed at the time.
The other non-British statesman commemorated hereabouts is Abraham Lincoln (1809-65) of whom there is a copy of the statue from St Gauden in Chicago. This is placed along with Canning's on the western perimeter of the square.

O/S Co-ords:3011.7962
Source(s):

Chambers Biographical Dictionary

The King's England London: The City and Westminster