CATSKILL, N.Y. — Late last year, Matthew J. Mosca, a specialist in historic paint finishes, gazed up at what looked like a scrap of wallpaper. It was jutting up from an old coat of red paint covering the walls of a pantry inside the yellow-brick farmhouse where the 19th-century artist Thomas Cole displayed paintings that revolutionized American ideas about art and wilderness.

But when Mr. Mosca climbed a ladder, he found it was not wallpaper, but a bold black decorative pattern known as a Greek key that had been hand-painted onto the plaster itself. Excited, he took this discovery to Jean Dunbar, a consultant in historic interiors who was working with him on the refurbishment of the Thomas Cole homestead.

By scouring Cole’s old paint invoices and his letters about décor, and comparing the design work with known sketches and paintings, Ms. Dunbar and Mr. Mosca deduced that the walls had been painted by the landscape master himself, probably around 1836. Meanwhile, Mr. Mosca unearthed yet more friezes on the walls of two parlors, possibly depicting leaves and roses.

The discovery of the paintings, hidden behind coats of wall paint for more than a century, were announced on Wednesday by Senator Chuck Schumer, Democrat of New York, who asked for federal grants to uncover and preserve them.