The MTBS project has mapped over 2,722 discovered fires covering over 11.8 million acres. Historically, all fire types were assumed to be wildfire (WF) unless they were specifically reported as a prescribed fire (RX) or wildland fire use (WFU) in the original source data. Since discovered fires had no original source data these fires fell into the default WF fire type category resulting in skewed reporting for the WF fire type. Over time, the cumulative impact of including discovered fires in the WF acreage has reached a point where it needed to be addressed. To correct this over-reporting the MTBS project has added a new fire type called unknown (UNK). The fire type associated with discovered fires has been changed to UNK throughout the MTBS data record (1984-2012) and will be reported as such in future data releases.