This Simulink model predicts the population of the United States over the course of the 21st century. Population is defined as a function of age and gender in the year 2010 based on US Census Bureau data. Birth, death, and immigration rates are also defined as a function of age and gender. A fixed rate projection is calculated, enabling the user to produce several demographic charts for the year 2100. MATLAB code is included to produce a population pyramid and animation showing population as a function of age over time. An aging population of 412 million is predicted.