[Ken H]

You are comparing estimates "300,000" with real numbers "400,000". The "400,000" number comes from records of prescriptions issued to both Union and Confederate soldiers during/after the Civil War.

These guys were civilians in 1880 and had dispersed around the country. How did they get such an accurate civilian count in 1880, but not in 1900?

[DiogenesLamp]

These guys were civilians in 1880 and had dispersed around the country. How did they get such an accurate civilian count in 1880, but not in 1900?

War records. Look it up. I'm pretty sure Confederate soldiers stayed in the South, and i'm pretty sure Wounded Union soldiers likewise stayed in the North, and very likely neither group moved around a lot.

Read up on "Soldier's Disease."

The Civil war is what started narcotic addiction in this country. Prior to that, few people knew of, or had access to, large quantities of narcotics.