Heat and Frost Insulators and Asbestos Workers Local Union No. 24's Territory consists of Washington, D.C., and the following counties in Maryland, Virginia, and West Virginia.
Maryland Counties: Washington, Frederick, Montgomery, Prince George's, Calvert, Charles, St. Mary's, Anne Arundel, Howard, Worchester, Dorchester, Talbot, Queen Anne, Kent, Cecil, Harford, Baltimore, Carroll, Wicomico, Somerset, Caroline, and Baltimore City.
West Virginia Counties: Morgan, Berkeley, Jefferson, Hampshire, and Hardy.
Virginia Counties: Frederick, Clarke, Loudoun, Shenandoah, Page, Warren, Fauquier, Prince William, Madison, Rappahannock, Westmoreland, Culpepper, Stafford, King George, Arlington, Fairfax, and the cities of Alexandria, Falls Church and Fairfax.