Wow! This is fantastic.
Above is a look at Ebbets Field on the day of the very first ballgame played at the stadium. Dated April 5, 1913, it shows a preseason exhibition between Brooklyn and their hated rivals, the New York Yankees. Pitching on the mound is Yankee hurler Ray Caldwell. Per Michael Claire at Cut4:
With 25,000 in attendance and 7,000 others watching "the game from the bluffs that loom above the field," Charles Ebbets had to turn away an additional 10,000 fans who wanted to catch the game. Though fans may have wished the park was a little larger, at least they didn't have to put up with the smell of rotting fish.