Tracing the development of the unilateral presidency is complicated because unilateral directives come in many guises. Many unilateral actions described in the press as executive orders are in fact presidential memoranda. Unilateral presidential directives do not give the president absolute or unchecked power. The constitutional silence invites the question of how it is that a practice that was never addressed in the Constitution or at the Constitutional Convention became such an integral part of the presidential arsenal. By the end of the nineteenth century, litigation relating to the president's power to withdraw public lands had led the Supreme Court to formulate several important propositions regarding unilateral directives. Although Congress and presidents had been reserving public land for public purposes since the beginning of the republic, before the Civil War few if any Americans gave any serious thought to reserving public lands in order to conserve the nation's forests.