High Quality Content by WIKIPEDIA articles! National Highway 51 (NH 51) is a National Highway of India in the states of Assam and Meghalaya. NH-51 starts from Paikan in Assam (at junction with NH 37) and ends at Dalu, in Meghalaya. The highway is 149 km (93 mi) long, of which 22 km (14 mi) is in Assam and 127 km (79 mi) is in Meghalaya.