SDCL § 9-45-6: Survey and plat filed on laying out or boundary change in street, alley, or public ground.

When any street, alley, or public ground in a municipality is laid out or its boundaries changed, the governing body shall cause an accurate survey and plat thereof to be made and filed in the office of the finance officer and in the office of the register of deeds of the county. Any municipality may widen an existing street within the platted right-of-way without filing new plats.