By the fifth century, the Angles (after whom East Anglia and England are named) had established control of the region. The Angles later became the "north folk" and the "south folk", from which developed the names "Norfolk" and "Suffolk". Suffolk and several adjacent areas became the kingdom of East Anglia, which later merged with Mercia and then Wessex.
Suffolk was originally divided into four separate Quarter Sessions divisions. In 1860, the number of divisions was reduced to two. The eastern division was administered from Ipswich and the western from Bury St Edmunds. Under the Local Government Act 1888, the two divisions were made the separate administrative counties of East Suffolk and West Suffolk; Ipswich became a county borough. A few Essex parishes were also added to Suffolk: Ballingdon-with-Brundon and parts of Haverhill and Kedington.
On 1 April 1974, under the Local Government Act 1972, East Suffolk, West Suffolk, and Ipswich were merged to form the unified county of Suffolk. The county was divided into several local government districts: Babergh, Forest Heath, Ipswich, Mid Suffolk, St Edmundsbury, Suffolk Coastal, and Waveney. This act also transferred some land near Great Yarmouth to Norfolk. As introduced in Parliament, the Local Government Act would have transferred Newmarket and Haverhill to Cambridgeshire and Colchester from Essex; such changes were not included when the act was passed into law.
In 2007, the Department for Communities and Local Government referred Ipswich Borough Council's bid to become a new unitary authority to the Boundary Committee. The Boundary Committee consulted local bodies and reported in favour of the proposal. It was not, however, approved by the Secretary of State for Communities and Local Government.
Beginning in February 2008, the Boundary Committee again reviewed local government in the county, with two possible options emerging. One was that of splitting Suffolk into two unitary authorities – Ipswich and Felixstowe and Rural Suffolk; and the other, that of creating a single county-wide controlling authority – the "One Suffolk" option. In February 2010, the then-Minister Rosie Winterton announced that no changes would be imposed on the structure of local government in the county as a result of the review, but that the government would be: "asking Suffolk councils and MPs to reach a consensus on what unitary solution they want through a countywide constitutional convention". Following the May 2010 general election, all further moves towards any of the suggested unitary solutions ceased on the instructions of the incoming Coalition government. In 2018 it was determined that Forest Heath and St Edmundsbury would be merged to form a new West Suffolk district, while Waveney and Suffolk Coastal would similarly form a new East Suffolk district. These changes took effect on 1 April 2019.
West Suffolk, like nearby East Cambridgeshire, is renowned for archaeological finds from the Stone Age, the Bronze Age, and the Iron Age. Bronze Age artefacts have been found in the area between Mildenhall and West Row, in Eriswell and in Lakenheath.
Many bronze objects, such as swords, spearheads, arrows, axes, palstaves, knives, daggers, rapiers, armour, decorative equipment (in particular for horses), and fragments of sheet bronze, are entrusted to St. Edmundsbury heritage service, housed at West Stow just outside Bury St. Edmunds. Other finds include traces of cremations and barrows.
In the east of the county is Sutton Hoo, the site of one of England's most significant Anglo-Saxon archaeological finds, a ship burial containing a collection of treasures including a Sword of State, gold and silver bowls, and jewellery and a lyre.