When Garden State Park opened this spring, it proclaimed itself "the race track of the 21st century."

Owner Robert Brennan unveiled a $100 million plant whose design was indeed bold and futuristic. Then Brennan challenged some of the sport's most established traditions when he lured Kentucky Derby winner Spend a Buck away from the Triple Crown series to compete for big money at his track.

But when Garden State's inaugural 66-day season ended Saturday night, the bottom line disclosed that the track was suffering from the same economic troubles that are plaguing 20th-century thoroughbred tracks.

Garden State attracted an average nightly crowd of 11,987, which generated a woeful average handle of $1.26 million. That wagering figure -- only slightly higher than Pimlico's -- was a far cry from what Brennan and his management had expected.

Brennan's enemies in the racing world probably are chortling over these figures, but they shouldn't be. Garden State's results show just how tough it is for any track -- even one with dazzling facilities and enlightened management -- to prosper amidst intense competition for the gambling dollar.

Garden State's physical plant may not have elicited unanimous rave reviews, but to anybody who has spent much time around the Maryland tracks it is a knockout.

It's fortunate the word "glitzy" has been added recently to the American lexicon or there wouldn't be an easy adjective to describe it. The plant abounds with neon and flashing lights. The glass-enclosed paddock, with tiers of balconies overlooking it, is a dazzling concept. The black-marble Phoenix Room is as elegant as any four-star restaurant.

Perhaps the most interesting aspect of the track's architecture, though, is that almost nobody watches races live anymore. Patrons standing on ground level can't see the backstretch, which is obscured by infield billboards. Patrons in the dining room can't see the track from their tables. But there are televisions everywhere (with superb picture quality) as well as a big matrix board in the infield, and that's how people watch the horses run. Very 21st century.

The enormous capital investment Brennan's stockholders made in the Garden State plant was to be the basis of a fascinating exercise in racetrack economics. Horseplayers are widely perceived as hard-core gamblers oblivious to esthetic niceties. So, the question was, would snazzy Garden State attract significantly more business than some ill-managed, drab concrete-and-glass box?

This was easy to measure, because Garden State draws from the same greater-Philadelphia area as Keystone Race Track, one of the drabbest concrete-and-glass boxes in the sport. When it operated from April to June in 1984, Keystone's average attendance was 6,500 and its handle $880,000. This was presumably the area's hard core, and its per-capita betting was $135 a day.

Garden State lured much larger crowds than Keystone without getting a much larger handle. Its new people were college students and social clubs and curiosity seekers who weren't betting seriously. Few major tracks in America have such low per-capita betting.

Garden State's challenge is to convert these new fans into enthusiastic bettors. Track President Robert Quigley said that when he was the general manager at the Meadowlands, that track's per-capita wagering was low in its first season but grew impressively as it created new horseplayers.

It is an article of faith among Garden State's management that this will happen in Cherry Hill, N.J., too. Brennan remains confident enough that he continues to commit big money to the operation; he already has raised the purse for next year's Jersey Derby to $2 million.

He explained: "Lee Iacocca doesn't build junk cars and hope people will buy them so he can turn a profit and then build decent cars. You've got to put in money from the start and look to the long term."

Despite Brennan's optimism and enthusiasm, the economic future of Garden State is uncertain. There is so much competition for the gambling dollar in the Northeast -- among casinos, state lotteries, illegal sports bookmakers and parimutuel establishments -- that the market may be nearly saturated.

Certainly, there aren't many thoroughbred tracks in the region that can boast that business is booming. But it would be a very ominous sign if Garden State does not flourish in the coming years. If a track with such splendid facilities and enlightened management can't prosper, who can?