Now that drug laws have become unpopular, there's an effort to rewrite history and blame it all on the Republicans, especially Nixon. It's surprising that this effort is so successful when the correct history is so easy to find:
Opium, coca, and their derivatives (including heroin) were made controlled substances by the Harrison Narcotics Tax Act of 1915 [1], a law sponsored by a Democrat and signed by Woodrow Wilson (a Democrat).
Marijuana was made a controlled substance by the Marihuana Tax Act of 1937 [2], likewise introduced in Congress by a Democrat and signed by Roosevelt, another Democrat. Roosevelt also publicly urged the states to legislate against "the narcotic drug evil." [3]
The Boggs Act of 1951 [4] introduced mandatory sentences for possession or distribution of both drugs. It was, you guessed it, also sponsored by (and named for) a Democrat in Congress, and was signed by Truman (D).
And even the relevant legislation passed during Nixon's term in office, the Controlled Substances Act of 1970 [5], was again introduced by a Democrat and passed a Democrat controlled Congress with bipartisan support. This law merely continued the prohibitions introduced by the previous laws after they were successfully challenged in Leary v. United States in 1969 [6].
1: https://en.wikipedia.org/wiki/Harrison_Narcotics_Tax_Act
2: https://en.wikipedia.org/wiki/Marihuana_Tax_Act_of_1937
3: http://www.druglibrary.net/schaffer/History/e1930/roosevelta...
4: https://en.wikipedia.org/wiki/Boggs_Act_of_1951
5: https://en.wikipedia.org/wiki/Comprehensive_Drug_Abuse_Preve...