This document provides an introduction and overview of the failures and costs of the War on Drugs in the United States. It discusses how prohibitionist drug policies have been ineffective at reducing drug use and have created unintended negative consequences. The economics of the illegal drug market, including high prices and profits, have incentivized crime and violence among suppliers. Over a trillion dollars have been spent on enforcement with little impact on drug use rates and harms may have been exacerbated by the criminalization approach. The "war" has largely targeted casual drug users rather than addressing problems of addiction and abuse.