So most criminologists will tell you that the War on Drugs is an utter failure. Drugs today are more potent and easily accessible than they were decades ago when this version of the War on Drugs started (Nixon > Reagan > Bush > Clinton).
Each one of these presidents worked to mobilize public opinion around a fear of both drugs and drug related violence (usually couched in some racialized or other stereotype such as hippies, mexicans, and the classic crack crazed black man). And each one is responsible for policies (usually in the form of massive federal grants) that helped states build more prisons, pay for crime/drug fighting technologies, put more police on the street, etc. that contributed to the massive growth of the police state in the US (for a visual art project documenting the growth of prisons in the US over the past few hundred years click here). Criminologists who study this stuff will tell you that this 'experiment' has been incredibly expensive (e.g., salaries for workers, health care expenses for inmates who are now staying in prison for much more of their lives). They'll also tell you that, in classic colorblind fashion, the war on drugs systematically surveys and punishes people of color and the poor, especially those living in urban settings. There seems to be a growing number of high profile figures and institutions calling for a change in the drug war. A couple of years ago Senator Jim Webb (D: VA) commissioned a Blue Ribbon panel to examine the war on drugs. The United Nations recently came out with a statement about the global war on drugs, Congress recently changed the 100:1 Powder/Crack Cocaine disparity to 18:1, and now former President Jimmy Carter wrote this op-ed in the New York Times. Check it out here.
Here's another report that documents the growth in the prison population (pg.1 ). It's also really important to keep in mind that the relationship between prison and crime is weak at best, but that's another post.