Built in 1824, The Workhouse, Southwell is the best preserved remaining example of the hundreds of workhouses built across the country. The system implemented at this workhouse was developed by the Reverend John T. Becher and George Nicholls, (later Sir George Nicholls), whose ideas shaped the way in which the poor were administered during the 19th century.

Becher's idea was for parishes to join funds and build a workhouse specifically to house the destitute rather than each parish giving individuals support in their own homes. Up to 158 inmates at a time, from 49 local parishes, who had nowhere else to turn, entered this building as a last resort. The adult poor were divided into categories - those unable to work (called 'blameless') and those capable of work but unemployed (considered 'idle and profligate ablebodied'). These categories were kept separate within the building and further subdivided into men and women. Children were separated into another group. These groups lived in segregated areas meaning families could not meet. They were fed, clothed, housed and some were made to work, and the children received a form of education.

Becher's view of the 'idle and profligate' was that workhouses should be a 'deterrent' and a 'test'; only the truly destitute would submit themselves to such a deliberately harsh regime. In this way The Workhouse would reduce the ratepayers' bills. It was also intended to achieve a 'moral' improvement, with the poor trying to provide for themselves if at all possible. However, children and the 'old and infirm' were to be treated tenderly.

Becher and Nicholls drew on over 200 years development of changing care for the poor since the 'Old Poor Law' of 1601. Their development and application of contemporary ideas to introduce a revolutionary but strict 'welfare' system attracted much attention. The Poor Law Commission investigated this model system before producing the Poor Law Amendment Act in 1834. Often known as the New Poor Law, this Act established a similar system nation-wide. Following the Act, hundreds of workhouses were set up across the country as part of a national government system, run from London offices. The workhouses provided for the poor of several parishes which were grouped into 'unions', so that many workhouses became known as union workhouses.

Becher's building, originally named the Thurgarton Hundred Incorporated Workhouse, was renamed Southwell Union Workhouse two years after the 1834 Act and brought into the national structure. For most of the 20th century it was known as Greet House, although workhouses were generally renamed 'institutions' before the 1st World War. In 1929 the New Poor Law system was disbanded and workhouses or institutions were handed over to local authorities. Most continued either as hospitals or, like The Workhouse, Southwell, as institutions to house the poor, homeless and elderly.

Once the modern welfare system was introduced in 1948, the building gradually evolved, providing temporary homeless accommodation until 1976. It was used mainly as staff accommodation and storage until the 1980s while the rest of the site was being used as a residential home for the elderly.

The importance of the building resides in its important historical role as prototype and its unusual survival of 19th-century workhouse features but also in the ability to demonstrate this later typical development of workhouse sites.