It was formed by the merger on March 27, 2006 of the towns of Hikari from Sousa District and Yokoshiba from Sanbu District. Sousa District was dissolved with this merger.
Yokoshibahikari features quite a unique topology: the town is a collection of quarters scattered over the large countryside extending from Yokoshiba's JR station on the Sobu Main Line to the (almost) 8km far coastline. Given such sparse structure, it takes quite a long time for the bus lines to serve the whole town.