The Insane Hospital of Augusta, Maine opened in 1840, but much of it burned down ten years later. Since there were so many insane people in Maine (they turned down 100 applications for lack of space) they rebuilt in 1854. By 1900 they had over 1,000 inhabitants.
I do not know when Charles Tower was admitted, but this drawing and fantasy story about the Albatross of Maine was certainly done before 1900. You can read it, but I think it made more sense to Charles than it will to you.
Letter and Drawing by Charles W. Tower, Augusta Insane Hospital circa 1880? Collection Jim Linderman