In 1986, congress passed the Anti-Drug Abuse Act in response to mounting fears, suspicions, and assumptions about crack cocaine (as opposed to powder). The death of a basketball player, who was thought to have OD'd on crack (he actually OD'd on powder cocaine), led to a lot of media attention, and congress passed the law in response.
At the time, there were beliefs that crack was worse than powder cocaine, causing increased crime rates, being more addictive, being more likely to cause psychosis/death, etc. Now, it is known that powder cocaine and crack cocaine are exactly the same pharmacologically: one gram of powder is equally potent as one gram of powder.
However, the law passed differentiated between cocaine and crack in an extreme and irrational manner, such that the penalty for possessing one gram of crack has the equivalent criminal sentencing of 100 grams of powder cocaine. As a result, the mandatory minimum prison sentence for 5 grams of crack (the weight of 5 sugar packets) is five years, while more than one pound of cocaine will result in that same sentence.
It turns out, the only real difference between crack cocaine and powder cocaine are the people who use it. Crack cocaine tends to be preferred by African-American drug users, while powder cocaine tends to be preferred by whites. The results of the law have been surprising:
"In 1986, before mandatory minimums for crack offenses became effective, the average federal drug offense sentence for blacks was 11% higher than for whites. Four years later following the implementation of harsher drug sentencing laws, the average federal drug offense sentence was 49% higher for blacks." -source
Additionally, "Most drug offenders are white. Five times as many whites use drugs as blacks. Yet blacks comprise the great majority of drug offenders sent to prison."-source
...And I don't really know quite what to make of this: "more than 80% of the defendants sentenced for federal crack cocaine offenses are African American, despite the fact that more than 66% of crack users are white or Hispanic."-source
And even when law officials realized the disparity between blacks and whites with incarceration soon after the law's passage, no action was taken. Today, it is still a law, although, finally, presidents (both Bush and Obama) and congresspeople have started speaking about the law, and preliminary new laws are present in both houses of Congress. (There is still a ways to go, however.)
Is it negligence that caused this to take so long? What are other laws passed under such irrational circumstances? Why is it possible for trends, craze, & suspicion to cause such devastating laws, yet scientific refutation and regret take forever to undo these damages? Why are African Americans overrepresented in the prison system for crack use more than other crack-using minorities?