Mo. Rev. Stat. § 300.270: Stop and yield signs.

1. The driver of a vehicle approaching a yield sign if required for safety to stop shall stop before entering the crosswalk on the near side of the intersection or, in the event there is no crosswalk, at a clearly marked stop line, but if none, then at the point nearest the intersecting roadway where the driver has a view of approaching traffic on the intersecting roadway.

2. Except when directed to proceed by a police officer or traffic control signal, every driver of a vehicle approaching a stop intersection indicated by a stop sign shall stop before entering the crosswalk on the near side of the intersection or, in the event there is no crosswalk, shall stop at a clearly marked stop line, but if none, then at the point nearest the intersecting roadway where the driver has a view of approaching traffic on the intersecting roadway before entering the intersection.