The unilateral presidency has been an important vein of research in the study of the American Presidency over the past two decades. Scholars have studied why and how presidents use certain unilateral directives during their administrations. Institutional constraints by Congress and the Courts have been the primary explanation for a president’s usage of unilateral directives. Few scholars have examined the effect that crises can have on these tools. Scholars have also primarily focused their attention on the use of executive orders and proclamations (to a lesser extent) in the post-World War II era. Few studies have examined how presidents before 1945 have used executive orders and proclamations. Using a dataset of over 2,500 directives, I examine when presidents, from 1861-2012, were more likely to issue significant executive orders and proclamations. In this dissertation, I empirically test my crisis theory of unilateral action. I test to see if crises cause presidents to issue more directives in the pre-modern era, modern era, and the full time frame. I also test the effect of the theory on these directives once they have been split into policy domains. I find that war and economic downturns cause presidents to issue more significant executive orders. Presidents issue more significant proclamations during economic downturns. War also causes presidents to issue more international executive orders, domestic orders/proclamations, and national sovereignty proclamations. Economic downturns cause them to issue more organizational orders, international orders/proclamations, and domestic proclamations. Natural disasters caused them to issue more domestic orders/proclamations and strikes caused them to issue more domestic proclamations. Overall, I find that presidential usage of unilateral directives is affected by certain types of crises and in some cases they have a stronger impact than the institutional variables.