Answer :
Coal is the natural source that was mind in the past century in Virginia.
The correct answer is coal.
The coal was produced in the carboniferous period by the deposition of the dead remain of the plant and the animals. The steamy swamps present at the time of carboniferous period allowed the thick peat to form, which eventually got buried in the ground and by the action of the heat and the pressure, the peat formed coal, which is mined now.