Two Roman villas stood within the later parish, one near the south-western boundary near fields called Chester Hill. The second, south-east of Low Ham, was begun c. A.D. 200 and extended c. 330, and was occupied until A.D. 367 or later. The ancient parish of High Ham, originally Ham, occupies the highest part of a ridge which forms the southern boundary of King's Sedgemoor and which runs from Aller in the west to Somerton in the east. The main settlement, High Ham, lies towards the northern edge of the ridge; Low or Nether Ham, the centre of an independent chapelry, occupies a terrace on the eastern boundary 2 km. SSE. Henley, which also had a chapel in the Middle Ages, lies just below the 15-m. contour on the edge of King's Sedgemoor, 1 km. N. and NE. of High Ham, and derives its name from meadow land below the scarp mentioned in a perambulation of the late 12th century or later. Beer, just above the 15-m. contour 1.5 km. WNW. of High Ham, is partly in Aller parish.
Most of the parish lies on a clay plateau, with limestone near the surface in places, largely above 76 m. and in the north-west above the 91-m. contour. From one edge of the plateau, at Turn Hill in the north-west, the land falls steeply over a narrow band of Keuper marl to a similar band of alluvium at the 15-m. contour and falls further, north-west and north, over the peat of King's Sedgemoor. North-east of High Ham village the descent to the moor is more gradual over Keuper marl. South-east of the village the clay plateau ends on a promontory called Sedgemoor Hill; south of the hill Keuper marl is followed by a gravel terrace where Low Ham village lies. The eastern boundary, with Pitney, follows a stream in a narrow band of alluvium and gravel.
The hamlet and mill of Paradise lies 2.5 km. S. of High Ham village, on the boundary with Huish Episcopi; and on the Langport- Somerton turnpike road is the hamlet of Picts or Picks Hill. The north-western and northern boundaries of the ancient parish, before the inclosure of King's Sedgemoor in 1795, followed the edge of cultivable land. The eastern boundary with Pitney is largely the Low Ham rhyne, which is followed southwards almost to the hamlet of Wagg in Huish Episcopi, forming a tongue of land occupying the eastern slope of Ham Down. The south-western boundary with Huish follows a watercourse above Wearne. The parish measures 7.5 km. from its northern boundary on King's Sedgemoor to the southern end of Wagg Drove and 4.5 km. at its widest point between Beer and Pitney Steart bridge. Archery butts were mentioned in 1527 in Barnard tithing. A duck decoy was dug in 1682, at a site later known as Pitney Gate. It seems to have gone out of use by 1726. The name is preserved in Decoy Farm.
Nine illegal ale sellers were reported in Barnard tithing in 1311, 14 in 1364, 16 in 1365, and 8 in 1418. There were no more than 4 from Netherham tithing between 1364 and 1418, and between 2 and 6 from Abraham tithing. Victuallers were in business somewhere in the parish in 1620 and 1732, and one at Beer in 1674. The How family had an inn called the Prince of Wales by 1788 and until soon after 1803, and the Thyer family were licensees of the King's Head by 1828 until the later 19th century. The King's Head was open in 2000.
High Ham village, the principal settlement by the Saxon period, includes houses around a green south of the parish church, a street running north and including the surviving inn and the village hall, a network of interconnecting lanes to the south-east and south, and others leading to the former common fields. Those fields, entirely surrounding the village, were inclosed in 1799. The green was mentioned in 1265, Green Street perhaps a little earlier, and North Street by 1667. New Street, part of Glastonbury abbey estate and containing building sites, was mentioned in 1369. Other sites for building, possibly to enhance land values, were mentioned several times between 1315 and 1529.
Low Ham village lies along three irregular lanes north and west of its surviving manor house and chapel. Henley Street was so named in 1667 but had building sites in 1350. Fields called Morton, NE. of Low Ham, indicate a so-called manor of that name mentioned in 1355 and furlongs named in 1779, all suggesting the former existence of a settlement. An unusually large number of houses survives from the 15th and the 16th century of which three are in Henley and three in Low Ham. Almost all the pre-19th century houses are of lias, either coursed rubble or squared, though Henley farmhouse may be built of cob. In the earlier ones the windows have timber lintels and probably had timber mullions; the superior later houses, such as the E-plan Manor farmhouse, High Ham, and the L-plan Dairy farmhouse, Low Ham, have stone mullioned ones. The roofs, originally thatched, have jointed crucks, which were still being used for some roofs in the 18th century, for example at Dobbins, Low Ham. Clay tiles appear after 1600 for new houses and reroofing, though thatch continued to be used in modest dwellings. Poorer quality rubble walling survives in 18th-century houses, and sometimes faces a cob core as at Poplar farmhouse, Henley. Slate for roofs and brick used alone or with stone for walling, as at Holly House, were introduced in the mid 19th century.
In 1563 there were said to be 60 households in High Ham and 19 in Low Ham; 67 households were recorded in the 17th century, and c. 1785 there were c. 113 houses and nearly 600 inhabitants. The total had increased to 713 in 1801 and rose rapidly to 1,027 in 1831. Further increases until 1851 were partly due to the presence of the Langport union workhouse in the parish. The total fell every decade until 1901, although the workhouse population also fell slightly from 1861 and sharply after 1881. In 1901 the population reached 898, rose to 958 in 1911 but thereafter declined, to 766 in 1931 and to 666 in 1951. By the last date the workhouse had closed, but the decline continued until 1961 or later and was thereafter reversed; in 1991 the total was 781.
The earliest houses were mostly of one storey plus attics. Most of those built after 1600 are two-storeyed but a few farmhouses, such as Poplar farmhouse, and cottages have one-and-a-half storeys. Although one or two houses are more complex, the usual pre-1650 plan has three ground floor rooms in line with a through passage, a form which continued in use throughout the 18th and early 19th century in about ten farmhouses built then, some with farm buildings in line. For their defence of Langport in July 1645 the Royalists took up a strong position on the east side of Ham Down, in the south of the parish. From there George, Lord Goring, and his men were driven swiftly back through the town by the New Model under Sir Thomas Fairfax. Richard Thomas, a Welsh soldier mortally wounded in the battle and found in a ditch, was buried at High Ham church.
Before the inclosure and drainage of King's Sedgemoor there was no land route north from the parish and its road pattern was a network of lanes linking High and Low Ham and subsidiary settlements and the fields, all approached from Langport. Access by water from the north was possible along a watercourse known by 1280 as Hardingsditch which was said to be a watercourse belonging to the abbot of Glastonbury linking High Ham with Pendon. It was still visible in the later 16th century. The Langport-Somerton road, passing through the southern tip of the parish and turnpiked in 1753, was also the principal route into the parish. By 1822 a road had been built across King's Sedgemoor to Pedwell via Henley Corner. In 1826 a variation of the same route, more directly north over Cradle bridge, was turnpiked by the High Ham and Ashcott trust, whose jurisdiction stretched along a single road from Meare to Picts Hill. The road was disturnpiked in 1879. A second route across the moor linking Beer with Othery had been built by 1885.
In the early 19th century private residences of fashionable form began to appear, particularly in High Ham village, including the Grange, a detached 3-bayed villa, ashlar-faced in Ham stone with a classical porch, and South End House, Field Road, of c. 1840, and, at Low Ham, Classeys. More were built after 1870, including the Gothic Wearne Wyche, north of Picts Hill, designed in 1875 by George Nattress for the Langport banker W. B. Paul, the French Gothic New Manor House in 1877, and Ham Court in 1906. The larger mid and later 19th-century farmhouses, such as the three-bayed Yew Tree farmhouse and Tibbs House, Henley, were also designed as genteel villas. Eight new houses were built between 1931 and the end of the Second World War.