Here are range maps of eight of the most common and important firs in North America. Two live naturally in eastern North America while the others' natural range is in the mountains of the North American west. Firs grow in cool, temperate regions and mountains south to Guatemala. Although not a true fir, I am also including Douglas-fir (Pseudotsuga menziesii) in this list for reader convenience.
Firs can be distinguished from Spruces by their upward-standing cones on top of branches. Spruce cones hang downward. Fir cones disintegrate on the tree while spruce cones fall to the ground. Fir needles are rather flat and two-ranked along branches while spruce needles are whorled around the branches.
Balsam Fir Range - USGS/USFS Map