OLD TOWN, Maine — When the last known owner of a plot of land on Treat and Webster Island seemed to have abandoned the property in the 1930s, some nearby residents claimed parts of it as their own. Now, they find themselves embroiled in a land dispute with the city over who really has rights to it. The land in question — known as lot 189 — sits along the southwestern end of the island, surrounded by the Penobscot River.