what made Opium addiction such a devastating factor in China's history is the fact that the substance is physiologically addictive to humans. But in America when opium was legal, addiction was low and declining. The DEA says, "In 1880 [...] there were over 400,000 opium addicts in the U.S. [...] By 1900, about one American in 200 was either a cocaine or opium addict." (http://web.archive.org/web/20110529221013/http://www.justice.gov/dea/demand/speakout/06so.htm) 400,000 in a population of 50M is one in 125 - ergo, between 1880 and 1900 addiction declined.
But in America when opium was legal, addiction was low and declining. The very link you cited says the exact opposite.
In 1880, many drugs, including opium and cocaine, were legal — and, like some drugs today, seen as benign medicine not requiring a doctor’s care and oversight. Addiction skyrocketed.
We also have this example from China.
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between 1880 and 1900 addiction declined.
Utterly false, but I expected no better from you. At best your research is poor, at worst it is a deliberate attempt to mislead.