premise: USS "Yorktown" (Gunboat No. 1/PG-1) was lead ship of her class of steel-hulled, twin-screw gunboats in the United States Navy in the late 19th and early 20th centuries. She was the second U.S. Navy ship named in honor of the American Revolutionary War's Battle of Yorktown.
hypothesis: Steel hulled ships were being built towards the end of the 19th century
reason: Yorktown was a steel hulled ship, and was active in the late 19th century, so it must have been built then. The sentence however has taken this information out of the context of the original phrase