By Brenna Angel, Kentucky Public Radio Thirteen historic sites across Kentuckyare now being considered by the National Register of Historic Places after getting the seal of approval this week from the state historic preservation review board. Among the latest round of nominees are several historic districts and structures across the state. Review coordinator Marty Perry says each site’s architecture and historical contributions are carefully analyzed.“So if a property is old enough – and it only has to be 50 years old to qualify, if it’s significant enough, and if it is intact enough, then we’ve got a property that’s a worthy candidate,” he said. The national review panel will make its decisions about the Kentucky requests within 45 days. The Bluegrass State has more than three thousand historic entries listed in the National Register.The sites include historic districts in Harrodsburg and Guthrie and structures in Bardstown, Murray and Bowling Green.