Erected in 1724, on the site of the Elizabethan market hall which it replaced, the building was designed to house two "Courts of Judicature" and a room for the Grand Jury at Assizes and Sessions. One of the most famous trials held here was that of the leaders of the Chartists, originally condemned to death but subsequently granted transportation to Van Diemen´s Land.
The present building was built in 1724 by William Rea and Edward Catchmayd on or close to the site of two previous buildings. The original building, built in 1536, was a small court but this was replaced in 1571 by a typically Elizabethan building with a timber framework with Philip Jones as architect, and Thomas Kerver and John Morys as builders. The timbers from the original building were used in the construction of the latter, which provided an open trading area on the ground floor with rooms above.
In 1708, land was purchased to extend the market hall and provide a council chamber and an office for the town clerk but no action was taken until the building of the existing Shire Hall in 1724.
Details of the cost of construction of the original building are not known. The cost of its replacement in 1571 was forty four pounds and the cost of the 1724 building was seventeen hundred pounds, sixteen hundred pounds of which was provided by the "County" and the balance by the Corporation (Borough). The furnishings in the form of tables, chairs, grate and railing were also provided by the Corporation. The architecture of the Shire Hall was very loosely in the popular style of the day - Baroque - and thought to be by Philip Fisher of Bristol. He lived for a time in a house in Monnow Street, currently occupied by Lloyds Bank.
The replacement of the Market Hall with a Shire Hall to accommodate assizes was mainly as a result of complaints that the Market Hall was not suitable as a market and that the original venue for assizes, the great hall in Monmouth Castle, was unsatisfactory through ill repair. Great Castle House was in fact used for assizes for a period immediately preceding the building of the Shire Hall.
Problems with the design and construction of the Shire Hall almost immediately ensued. In 1743 major renovation was undertaken by Philip Hardwick of Bristol, a friend of Philip Fisher no less, at a cost of three hundred pounds. Further additions were made to the building in the form of a clock in 1765, by Richard Watkins, and railings by Peter Embury in 1767. The statue of Henry V, who was born in Monmouth Castle in 1387, was added in 1792.
Further problems were encountered with the building and in 1821 a committee was set up to look into them. The result was that in 1829 royal assent was given for improvements under the direction of Thomas Hopper. This work carried out through Edward Hayock, included the construction of a new staircase, larger courts and the extension of the building along Agincourt Street.
Building work was completed in time for the opening of the assizes in 1831 at a cost of just over seven thousand pounds, which in spite of a brief to provide "comfort" for the judges included a mere one hundred and forty three pounds for furnishings. At this time plans existed to re-house the market but it was not until 1837 that all trading, with the exception of corn, flour, wool and hops, was transferred to the new Market Hall in Priory Street.
The Shire Hall has continued to provide the services to which it was designated to this day, with several notable exceptions i.e. the magistrates court was transferred to the Market Hall and is now held in Abergavenny. The general trading market has returned, although not in corn, flour or wool, on Fridays and Saturdays. Whilst assizes are now held at various locations they are convened in the Shire Hall court room approximately six times a year. Monmouth Gaol was closed in 1869 and as a result the assizes became considerably smaller than previous. The room now referred to as the community room at one time housed the town's library, which is now located in the Rolls Hall. The railings between the arches were removed as part of the war effort during the Second World War. The statue of Charles Rolls, who had the dubious distinction of being the first English aviator to be killed in the air, was unveiled in 1911.
The most notable event to take place at the Shire Hall was, following the Newport riots, the trial in 1840 of the chartist John Frost, who along with Zephaniah Williams and William Jones was convicted of High treason and sentenced to be "hanged until dead and quartered". History has it that a Monmouth doctor offered to do the quartering. Whilst the gallows were being built on the roof of Monmouth Gaol within earshot of the condemned cells, the sentence was commuted to deportation. Frost was deported to Tasmania (Van Dieman's Land), given a provisional pardon in 1854, fully pardoned in 1856 and returned to England where he died in Bristol in 1877 at the age of 93. The trial of Frost and his 11 other co defendants took but a matter of a few weeks (starting on New Years Eve with sentences past on the 16th January) and attracted the most senior judiciary in the form of the lord chief justice and was clearly highly political. The jury took less than an hour to reach a guilty verdict. The cost of the trial was seventeen hundred and forty four pounds, which included one hundred and twelve pounds for London policemen.