The U.S. Geological Survey's National Coal Resources Data System comes with an interactive map that provides a huge amount of information on the distribution, thickness, and classification of coal in the United States.
The interactive map contains over 250,000 data points, each typically representing a core sample, drill hole, or driller's log in a specific location. You can use the "Filter" tool to focus in on specific areas, or on data collected by specific organizations. Commonly available data include: