Minn. Stat. § 240.29: REQUIRED RACES.

Each holder of a class B or D license must declare and schedule, on each racing day it conducts, at least one race which is limited to horses which are Minnesota-bred or Minnesota-foaled.

If there is not a sufficient number of such horses entered in the declared race to make up an adequate slate of entries, another similarly restricted race may be substituted.

The commission shall by rule define "Minnesota-bred," "Minnesota-foaled," and "Minnesota-owned."