http://fitzhenrylaneonline.org/homepage.php
Fitz Henry Lane (AKA Fitz Hugh Lane) turns out to be a good visual source for square rig ships. Good old Fitz painted the ships around him in New England in all sorts of settings during a time when Gloucester and Boston were top Atlantic harbors. There is a smattering of paintings from New York harbor, then as now THE major eastern seaboard port.
I unearthed this site while exploring via Google how square-riggers handled fore-and-aft sails in port - that is, staysails, jibs, spankers and so on.
From Wikipedia's entry for Fitz:
"From the time of his birth, Lane would be exposed to the sea and maritime life—a factor that obviously had a great impact his later choice of subject matter. Many circumstances of his young life ensured Lane's constant interaction with various aspects of this maritime life, including the fact that Lane's family lived "upon the periphery of Gloucester Harbor's working waterfront,"[3] and that his father, Jonathan Dennison Lane, was a sailmaker, and quite possibly owned and ran a sail loft. "
His marine paintings date from the late1830s to his passing in 1865. As a source, then, he's probably good for practices during the first half of the 19th Century... many of which carried over from the 18th C.
His works are in the European Academic style, meaning that there is great deal of attention to detail and, presumably, a great deal of accuracy in what you see in his paintings. Again, from Wikipedia:
"Perhaps most characteristic element of Lane's paintings is the incredible amount of attention paid to detail—probably due in part to his lithographic training, as the specific style of lithography that was popular at the time of his training was characterized by the goal of verisimilitude."
The site's collection of his works is under The Catalog > Works in the Catalog. You access a custom search utility from a box just under the page heading, "The Catalog of Paintings, Drawings, and Lithographs."
Selecting "harbor scenes," I was able to find 9+ premo images that clearly depict a range of furling, half-furling, and sail setting for both the square sails and the fore-and-aft ones, and probably 20 more that provided one additional detail or another.
As for rigging, I'm not enough of an expert to know if his depiction of rigging is highly accurate. I'm assuming that it is accurate - he was around ships from his birth to his death.
And obviously, I don't know the evolution of rigging practices, so I don't know how transferable his depictions are to earlier times - or what about them might tell me volumes about 19th C practices... if I just knew enough...