Elsecar Iron Works
Also known as Darwin Iron Works.
1795 Established by the partnership of John Darwin, William Darwin, Francis Frith and Joseph Ridge.
In 1796 the company began mining ironstone from Fitzwilliam lands at Tankersley, first in Tankersley Park and later at Westwood. They had extensive involvement in iron and mineral businesses across South Yorkshire, starting in Sheffield, and in Chapeltown as well as Elsecar and Worsbrough from around 1812.
1817 William Darwin was declared bankrupt.
1823 Joseph Ridge left the partnership.
1827 Bankruptcy of Darwin and Frith.
The Elsecar works were taken in hand by Earl Fitzwilliam as landlord, who put Henry Hartop (1785-1865) in charge.
Control later passed to his son, John Hartop (1815-1902) who maintained the business on behalf of the 5th and 6th Earls Fitzwilliam as proprietors until the Elsecar and Milton works were leased to a new partnership in 1849.
The above information is condensed from the Friends of Hemingfield Colliery website 
The ironstone was mined close to Elsecar, although the best ironstone came from Tankersley. Darwin & Co. sold pig iron and made domestic ranges, rails for colliery tramways, window frames and arches which can still be seen on various buildings around the Elsecar site.
1860s The Elsecar Iron Works were the most famous in South Yorkshire at that time but later ceased operations and were dismantled.
1885 "...During the past week the last ray of hope in connection with the establishment of the old and well-known Elsecar Worn. near Barnsley, has vanished. The work, which were replete with valuable machinery for the purpose of producing sheet, rodand bar iron, in addition to other kinds of work, have been carried on by Mr. G. Dawes, the property belonging to Earl Fitzwilliam. The lease expired at the close of last year, and not being renewed; the machinery and plant were dismantled, the hammer beds being blown up with dynamite..."