"They mark our passage as a race of men,
Earth will not see such ships as these again."
Inscription on the "Cutty Sark", Greenwich, England
Joseph Conrad, who wrote novels featuring sailing ships, said:
"The last days of sailing ships were short if one thinks of the countless ages since the first sail of leather or rudely woven rushes was displayed to the wind. Stretching the period both ways to the utmost, it lasted from 1850 to 1910. Just sixty years. Two generations. The winking of an eye."
However, Conrad's stretching of the period could have been stretched to a further utmost. The last whaling voyage by the New England Whaler Charles W. Morgan was in 1921. (The ship, built in 1841, is still preserved in Mystic Seaport, Connecticut)
http://www.mysticseaport.org/visit/explore/morgan/
As r/hiding-in-the-corner commented, the Australian grain trade and the Chilean nitrate trade were still carried on under sail between the two world wars.
The last great commercial windjammer was the "Pamir", which went down in a hurricane in 1957.
The Pamir was a four masted barque, built in Hamburg in 1905.
In 1949, sailing for the famous Erikson line of the Aaland Islands of Finland, she was the last windjammer to carry a commercial cargo around Cape Horn.
The Eriksons found they could no longer operate the ship profitably due to regulations and union contracts requiring that the traditional two watch system be replaced by a three watch system (needing a larger and more expensive crew), so she was sold to a German consortium who operated her carrying cargo to the East Coast of South America, crewed by sail training cadets.
So, from 1952 she was a cargo carrying school ship. In 1957, she went down in a hurricane, with only 6 of her complement of 86 surviving.
http://en.wikipedia.org/wiki/Pamir_(ship)
That was the last of commercial sail by the great ocean going windjammers.
There was still some commercial sail by smaller vessels in the Caribbean and South Pacific, but the age of commercial sail by the great windjammers engaged in deep sea trade was finally gone, 47 years after Joseph Conrad had declared it dead.
Pacific Lumber Schooners were built along the US West Coast. I can't find the number built but I think it was in the low hundreds.
Two, including Wawona and C.A. Thayer, were used for hauling lumber from the 1890s to the 1910s, mostly up and down the North American West Coast but sometimes overseas, and then for fishing up until around 1950. Wawona was scrapped recently and C.A. Thayer remains a museum ship in California.
Here is a book about these vessels: http://www.amazon.com/C-A-Thayer-Pacific-lumber-schooners/dp/B0006YQXCE
They were followed by steam schooners, such as the SS Wapama.