In the eastern part of the region lie the Hauraki Plains, best conceived as a shallow scoop draining towards the Firth of Thames by means of the Piako, Waitoa, and Waihou Rivers. The eastern and higher boundary is formed by the hills of the Coromandel and Kaimai Ranges which reach their highest point, 3,126 ft, close to Te Aroha. The western boundary is a lower, less distinct, and less continuous ridge which, nevertheless, rises to over 1,500 ft and abruptly contrasts with the lower lying land of the plains. The plains are dominantly a dairying region, with more fat-lamb farming included in the southern and western parts, and hence they have a characteristic landscape created by close subdivision, hedgerows, tar-sealed roads, and the close proximity of houses. Near Paeroa, in the central part of the plain, a large area of peat land remains undeveloped, and is used as a ponding area at flood time. Apart from a few small settlements, usually grouped round one of the large dairy factories, a number of small boroughs act as marketing and servicing centres for the surrounding communities. Of these the largest is Morrinsville, with a population of 4,111, followed by Matamata (3,298), one of the fastest growing towns in the region, and Te Aroha (3,060), the slowest growing town. Putaruru, which is situated at the southernmost part of the region, had a population of 3,551 in 1961, compared with 1,040 in 1945. This rapid growth has been associated with the development of the timber and agricultural resources of the Central Plateau, with whose fortunes those of Putaruru are more closely linked. This is even more true of Tokoroa, which, although located in Matamata county, is economically part of the Central Plateau. It owes its growth to the development of the pulp and paper industries at Kinleith. The town in 1951 had a population of only 1,193, but 10 years later it had reached 7,104.

The upper part of the Thames Valley around Matamata, being better drained, was settled much earlier than the low-lying, wetter districts of the Hauraki Plains. After the Maori Wars, exceedingly large estates were established on the light volcanic soils. The Matamata estate extended over 50,000 acres and, in 1899, carried 41,000 sheep, 2,600 cattle, and 184 horses, while 2,000 acres were under root crops and 500 under oats. About half the property was under scrub, fern, and undrained swamp. Eventually these large properties were broken up into smaller farms, either through private purchase and leasing or because of State intervention. The settlement of the Hauraki Plains occurred after the Act of 1908 which promoted the draining and settlement of 90,000 acres of Crown land. Previously the area was a morass and, even to the present period, a short length of railway line by which the milk cans were carted over the wet ground from the milking shed to the road remained a distinctive feature of the district. It was in these areas, especially, that the widespread use of concrete created a minor revolution in the housekeeping problems of farming wives.