Mark McGwire baseball cards are some of the most popular in the world, and as such, they can be worth a lot of money. The most valuable McGwire card is his rookie card, which was released in 1985. This card can sell for hundreds or even thousands of dollars, depending on its condition. Other popular McGwire cards include his 1986 Fleer Update rookie card (worth around $100), his 1987 Topps Traded rookie card (worth around $50), and his 1989 Upper Deck Ken Griffey Jr. rookie card (worth around $40). All of these cards are worth considerably more than their original value, making them great investments for collectors.bb