the English hypothesized that the Pacific Ocean coastline visited by Sir Francis Drake was a 10-day march west of the James River's headwaters
Source: Library of Congress, A mapp of Virginia discovered to ye hills, and in it's latt. from 35 deg. & 1/2 neer Florida to 41 deg. bounds of New England (1657 revision by Virginia Farrer of 1651 map by her father John Farrer)
The first permanent European settlers at Jamestown were not satisfied with the Algonquian descriptions of inland Virginia. It was quickly evident that the Native Americans in Tidewater Virginia had not gathered mineral wealth and jewels equivalent to the riches discovered by the Spanish in Central and South America, but there was always the possibility that further exploration would reveal gold and silver.
The Europeans had crossed the Atlantic Ocean for wealth, and were willing to take great risks in order to discover it. John Smith discerned the "lay of the land," including the political relationships among the native tribes, in hopes of finding valuable resources. The investors who had funded the expedition to Jamestown expected a profit, and Smith hope he too could benefit from whatever was discovered - though his extensive explorations and mapmaking suggests he may have been driven by an unuusually strong curiosity as well.
Despite the objections of Powhatan, the English explored across the Fall Line within the first year of settlement. They met the Siouan-speaking Manahoacs upstream of the future site of Richmond, and engaged with other tribes who lived up the Rappahannock River. Smith led two journeys in 1608 up the Chesapeake Bay, even meeting the Susquehannock at the northern edge.
The English dreamed of finding a route to China, the fabled Northwest Passage that would bypass the Caribbean controlled by the Spanish. Trading with Native Americans offered an alternative way to acquire wealth, through acquisition of deerskins. One early plan was limited by the creation of the Maryland colony, which blocked William Claiborne from maintaining or expanding his fur trading empire on the upper Chesapeake Bay.
The lack of roads meant that only small, easy-to-transport items such as deerskins could be carried far distances. Still, merchants such as Abraham Wood sent exploring parties far to the west.
There were always military reasons for exploring the "unknown" western lands, and interest in inland areas increased as Tidewater Virginia was settled. Indentured servants who had completed their term of service settled on new lands to the west, gradually pushing the border between colonist-Native American control upstream. The emerging Virginia gentry sought data on where land was worth accumulating through government grants.
After the end of the Third Anglo-Powhatan War in 1646, fur traders explored southwest of the Appomattox River. Edward Bland and Abraham Wood traveled from Fort Henry (modern Petersburg) in 1650, spending nine days in the backcountry in hopes of developing a trading relationship with Native Americans living on the Piedmont.
Abraham Wood established at fur trading fort on the Appomattox River, and explored south and west into the Roanoke River watershed
Source: Library of Congress, Virginia and Maryland as it is planted and inhabited this present year 1670 (by Augustine Herrman)
In the 1670's, Virginia explorers crossed the Blue Ridge. By the time Governor Spotswood led an expedition to the Shenandoah River in 1716, the journey was so safe that the trip resembled a party more than a challenging adventure. Starting in the 1730's, Governor Gooch began issuring land grants to settlers willng to occupy lands west of the Blue Ridge, creating permanent settlements deeper in the territory still claimed by various Native America groups.
The names of the earliest explorers who first moved through the Blue Ridge passes are not recorded in any historical documents. Today we have to use our imaginations to appreciate their travel through virgin territory, as far back as 15,000-20,000 years ago. It must have been far more difficult than the expeditions of the English just 400 years ago.
Many of the earliest colonial-era explorers during the 1600's and 1700's are also undocumented. Escaped servants and slaves moved past the boundaries of colonial settlement, obviously without sending official reports to Jamestown or Williamsburg. For example, when surveyors marked the boundary between Virginia and North Carolina, they encountered former servants and slaves who had entered the swamps in the southeast previously in a search for freedom.
the map published in 1754 with The Journal of Major George Washington showed Virginia's claims westward to the Mississippi River
Source: Wisconsin Historical Society, Map of the western parts of the colony of Virginia as far west as the Misssissippi (1754)