The National Priorities List (NPL) contains the most serious uncontrolled or abandoned hazardous waste sites throughout the United States and its territories. The NPL lists sites after 1) completing a Hazard Ranking System (HRS) screening and 2) soliciting and addressing public comments about the proposed site.
The NPL guides the federal government in determining which sites should be investigated. It is updated on a regular basis.
The EPA designates several NPL statuses for Superfund sites: Proposed, Final, Deleted, Withdrawn, and Removed. Not all Superfund sites are considered national priorities by EPA, and so do not appear on the NPL. TOXMAP contains data only on sites designated as Final (currently on the final NPL), Proposed (proposed for the NPL), and Deleted (deleted from the final NPL). These three statuses are collectively referred to by the EPA as the "NPL Dataset".
For details about the NPL site listing process, see this EPA page.