I doubt there would be that many more users, as it is, they just congregate where the rules are more lenient, or where they can make the most money (where the rules are strict). We didn't have those laws before 1900 and the country just fell apart, right?
NO!!!! <gasp!>
Do we have statistics on countries that have fully legalized drugs? What were the effects on crime and people?
Also, what drugs were easily available in early America? I know that alcohol use was very popular in the early 19th century America.