Circa 1910 Pre-Linen Postcard of the Polo Grounds with an Inset of John McGraw. Lot 314. Circa 1910 Pre-Linen Postcard of the Polo Grounds with an Inset of John McGraw. This version of the card is titled “Polo Grounds, National League Baseball Park, New York.” It is unnumbered and lists the seating capacity of the Polo Grounds as 45,000. Vg. Winning Bid $20. Back to List Winning Bid $20 Back to List