By 1614, the English settlers had occupied much of the land along the James River and were beginning to establish farms on the York River. The territory controlled by Powhatan was reduced as the English expanded out from Jamestown. The Algonqian ruler was forced to move west from his original capital at Werowocomoco to Orapakes in 1609, and ultimately Powhatan settled at the headwaters of the Pamunkey River at Matchut.
According to Helen Rountree,1, the move occured between 1611 and 1614. The new location offered better water access for Powhatan to receive corn provided by his subordinate werowances, and offered better farmland for local production compared to the hills and swamps or Orapakes.
Most importantly, Matchut was far enough away from the English for Powhatan to feel secure. It was located on the northern bank of the Pamunkey, in a location where the English could not reach by sail before the Native Americans recognized the threat of a potential water-based attack. Locating Matchut on the northern bank of the Pamunkey also put another water barrier between the capital of the Algonquians and the English, providing some protection against a ground attack.
While more secure, we know that Matchut was accessible to the English. According to Ralph Hamor, Matchut was a two-day trip from Bermuda Hundred on the south bank of the James River. In 1614 he visited Powhatan to negotiate a marriage between Sir Thomas Dale, the leader of the English Colony, and one of Powhatan's daughters. 2
Dale hoped such a marriage would bring an end to the Anglo-Powhatan wars. After Powhatan rejected the proposal, Dale tried to pressure Powhatan by bringing Pocahontas to Matchut and renew Dale's offer to exchange her in return for the settlers that had fled to the Algonquian towns and for the English tools and weapons they had stolen.
Dale sailed with 150 men to the Pamunkey River, where according to Hamor's account (obviously written from the English point of view, with phrases such as "justly provoked"):
Obviously Matchut was not inaccessible to sailing ships.

When Powhatan moved the confederacy's capital moved to Matchut, his younger brother Opechancanough lived across the Pamunkey River at Youghtanund. When the Algonquian chief died in April 1618, his younger brother Opitchapam assumed authority. However, it appears Opechancanough controlled the confederacy's dealing with the English. Opechancanough organized the Great Uprising of 1622, when the Algonquians dropped the appearance of peaceful coexistence and attacked the English settlements.
The English response to the Great Uprising, and to another one in 1644, was to kill or displace most of the Algonquians living in Tidewater and destroy the Powhatan Confederacy. Today there are seven recognized tribes in Virginia with ties to the original confederacy, including two with reservations on the Pamunkey and Mattaponi rivers, but the last "capital" of the organized confederacy was apparently Matchut.