At its core, border security means the control of people,goods and conveyances traveling across land, sea and air international boundaries. Border security has been on the national agenda since the United States was founded. As new concerns and threats have developed over the last 235 years, so too have the agencies responsible for executing the border security mission.  This monograph looks at the evolution of border security agencies and missions leading up to the terrorist attacks of September 11, 2001, and examines the offi cial response to those attacks. The paper surveys how industry is supporting U.S. efforts to enhance border security, and discusses future challenges.  Read the monograph.