The 400,000 addict number comes from perscriptions written by Union and Confederate doctors regarding the dispensation of painkillers. This addiction later became known as "the soldier's disease."
You don't have any good numbers, but you have to be a special class of fool to believe that cocaine laced carbonated beverages (Coca-Cola) would not cause deep and widespread addiction.
So you keep claiming although the only available numbers say the opposite.
The 400,000 addict number
One number can't establish a rise. And your one number agrees with the DEA numbers I've been citing.
You don't have any good numbers
As you've said, "Till someone presents an argument that there are better figures, I will have no choice but to use what is available." What's available, from the DEA, says that addiction was low and declining in post-Civil War America: "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.