SDCL § 31-13-15: Road districts.

Each organized township may divide the roads or streets in the township into road districts which shall include not more than:

(1) One-half mile of township road which provides access to a rural subdivision or unincorporated town;

(2) Three miles of streets in an unincorporated town; or

(3) Five miles of streets in a rural subdivision as defined in § 31-13-32.