1945 – Scheduled demonstrations at the Polo Grounds and Ebbets Field to end segregation in organized baseball are called off.

This Day In Baseball

On August 18, 1945 — 1945 – Scheduled demonstrations at the Polo Grounds and Ebbets Field to end segregation in organized baseball are called off.

Source:
Baseball Reference August 18
National Pastime
Retro Sheet
Hall of Fame
SABR Games Project
Replay The Game