Castleton is a heavily commercialized neighborhood located in the U.S. state of Indiana. It is within Lawrence and Washington townships of Marion County encompassing the original southern terminus of Interstate 69 on the northeast side of Indianapolis adjacent to the Geist and Clearwater areas. It coordinates at 39°54′25″N 86°03′08″W. Lawrence North High School, Community Hospital North and Community Heart and Vascular Hospital reside in Castleton. It has own post office using Zip codes 46250 and 46256.