Here are four historic homes that have been for sale for a conspicuously long time. They include a very historic 1798 National Register property in Forsyth County, an 1870 house in historic Milton, an intriguing 1898 mansion in Troy and a 1925 mansion in Greensboro’s Irving Park.

There are a variety of reasons why thy haven’t sold. Some are obvious — $600 per square foot is awfully high for any house, and Milton and Troy are a little remote from the hotter real-estate markets in the state. But the Greensboro house is a mystery. Click on the links for the complete listings.