One of the most surprising aspects of the rookie card renaissance, which has evolved over the past three years, is the emergence of forgotten cards and sets. Sets once described as "junk" are now the treasure chests of the hobby.

Two years ago, 1990 Score Rising Stars sets weren't worth the paper they were printed on. The product was just another casualty of the late '80s and early '90s overproduction years. Dealers had cases of the set, as well as dozens more similar sets, gathering dust in their back rooms. But then, during the 1998 baseball season, something wonderful happened -- Mark McGwire and Sammy Sosa started to hit home runs.

And they hit a lot of them.

The baseball card hobby was revitalized. Old collectors who had stopped collecting returned energized, and new collectors were drawn to the excitement. Everyone wanted a piece of history, but history came at a price. A lot of collectors were shocked at the costs of McGwire and Sosa rookie cards. At the peak of the home run chase, McGwire 1985 Topps rookies were selling between $300 and $2,000. Sosa rookies from 1990 Leaf started in the $80 to $100 range. For many, those prices were too steep. Collectors began looking for other options.

The only true Mark McGwire rookie card is from the 1985 Topps set. Other cards, which claimed to be rookies, came along in 1987 when Big Mac joined the major leagues. But the '85 McGwire card is the one that's technically the first. For rookie card collectors, it's the only option. Sosa, on the other hand, was featured in numerous sets after his 1989 rookie season. Collectors had mostly focused on the '90 Leaf card -- it's a high-quality card from a low-production set. But Sosa rookies could also be found in the 1990 Bowman, Donruss, Fleer, Score, and Topps sets. They were affordable (around $5 each) and dealers had tons of it. It was "junk." And it was just the tip of the trash heap.

Smaller sets, like the 1990 Score Rising Stars set and the 1990 Topps '89 Debut set, also featured Sosa rookies. But because almost no interest had been directed at these sets for so long, years of neglect had created a demand. Today, these sets are some of the hottest items on the market.

Forgotten sets continue to emerge out of dusty back rooms. Examples include the 1989 Score Rookie/Traded set, featuring rookies of Ken Griffey Jr. and Albert Belle; the 1987 Donruss Opening Day set, which includes early cards of Jose Canseco and Barry Bonds; and the 1991 Upper Deck Final Edition set, highlighted by the rookie card of 1999 AL Cy Young award winner Pedro Martinez. Until Martinez' MVP-worthy season, the Final Edition set was arguably one of the worst Upper Deck products ever produced. One dominant season, however, turned everything around.

The hobby still has plenty of "junk." In fact, a number of recently produced sets may qualify. But it's the "junk" that provides some of the greatest highs that the hobby has to offer. Any collector who's ever discovered a gem in their commons box can identify -- a set may seem worthless now, but in ten years, you may find yourself pleasantly surprised.