How many historic districts does Houston have?

Houston has the following 22 Historic Districts: Audubon Place, Avondale East, Avondale West, Boulevard Oaks, Broadacres, Courtlandt Place, First Montrose Commons, Freeland, Germantown, Glenbrook Valley, High First Ward, Houston Heights East, Houston Heights South, Houston Heights West, Main Street Market Square, Norhill, Old Sixth Ward, Shadow Lawn, Starkweather, West Eleventh Place, Westmoreland, and Woodland Heights. The attached HAR link will provide you with detailed information on each historic district such as information about the district, boundaries and maps, history and culture, architectural styles, defining features of construction, the setting requirements of buildings, information on Certificates of Appropriateness (COA), and information about Landmarks (LM) / Protected Landmarks (PLM) / Archaeologic Sites (AS).
http://www.har.com/historic_districts
http://www.houstontx.gov/planning/HistoricPres/HistoricPreservationManual/hist_dist.html