Jamestown, in modern-day Virginia, is important as it was the first permanent English settlement in North America. There had been a number of previous efforts by the English to establish American colonies, but for one reason or another they all failed. Nevertheless, the dream never died, and the the colonial ideal was one that captured the imagination of countless Englishmen, who saw in the New World an opportunity to make themselves incredibly rich.
And so the Virginia Company, granted permission by King James I of England, established Jamestown—named after the king—in 1607. The site of the new colony was chosen for a number of reasons. First and foremost, it was relatively easy to defend against marauding Spaniards, who at that time had a number of colonies of their own in North America and wouldn't have taken kindly to their hated enemies taking great chunks out of their territory.
An added advantage to the chosen site was that it wasn't already inhabited by the native population. Though ironically, it was a local tribe, the Powhatan, which came to the rescue when the English settlers began to be struck down by disease and starvation. But even their assistance wasn't enough to prevent something like 80-90% of the Jamestown settlers dying during the first three years of the settlement's existence.