…Are you aware that there is a passenger record for:
James Melrose, age 22, Draper(?) - sailed to New York on board the Columbia, arriving 3 Sep 1869 (port of departure was Glasgow, Scotland).
Could this be John’s son? I wonder if John was in America at that time?
I saw a passenger list for whom could be Mary and James, arriving in America in 1907, they were shown as American citizens, I believe. That led me to look for James’ earlier sailing date.
I hadn't seen the record for James, but he would have been only 14 in 1869, so I don't think this is him. In the 1910 federal census, it says he immigrated in 1882, and I have found him so far in the 1895 and 1905 New Jersey censuses as well. He was a merchant, starting his own businesses in Trenton, marrying Gertrude Sittner in 1898.
Thanks again!
Looking at the newspaper article that RJ137 found, dated 1911,
“Mr. Melrose retires after 40 years of business activity.”
Forty years could mean 37 or 38 years or it could mean exactly 40. Was his business activity split between Scotland and America or solely in America for 40 years?

1911 - 40 = 1871. I wonder if he did sail to America in Sep 1869, perhaps following his father or another relative?
However, I believe he was in Scotland in 1871 — did he sail in 1869, return to Scotland (for some reason) in time for the 1871 census and return to America after the census?
I will look again for John, or any Melrose, sailing c1869.
Update: sorry, forgot that James age in 1869 was recorded as 22. Can’t be him unless he lied about his age/it was recorded incorrectly.