In Interior Alaska, firelines are often constructed to help control and contain wildfires. In the early 1960's and early 1970's, the firelines were built, as in the western states, by tractors with bulldozer blades that scraped off the organic mat, knocked down trees, and pushed all material to one side of the line. The tractors worked back and forth across the fireline until mineral soil was exposed. Usually, most of the developed soil was removed with the organic mat. Firelines often were built on the easiest route between two points where the lines could be constructed most rapidly. Slope, aspect, and soil condition on the route were considered primarily in relation to fire suppression effectiveness rather than permafrost, potential erosion, or reclamation problems and solutions.