There are two significant omissions in the literature on presidential unilateralism. First, few scholars have examined whether their theories apply to directives other than executive orders. Second, scholars have primarily focused on unilateral usage in the modern era at the expense of the traditional era. This article addresses these omissions by testing one theory, Howell’s Unilateral Politics Model, on the usage of more than 1,300 significant executive orders and proclamations from 1861 to 1944. The results show that presidents in the traditional era issued more executive orders during a partisan administration change and that this effect continued into the modern era. Traditional presidents also issued more proclamations when Congress was stronger, which is counter to what Howell expected in his theory. Ultimately, these results show that the traditional–modern presidency dichotomy applies for proclamations but not for executive orders. The modern patterns of executive order usage are a continuation of the patterns that began in the traditional era. However, a noticeable shift in behavior occurred between eras with respect to presidential proclamations, probably as a result of this type of directive evolving from an administrative tool to a more unilateral order.