Anyone who visited Columbia, Maryland, early this week without knowing what was afoot might have thought he'd wandered a decade or so into the past rather than into James Rouse's vision of the future. There were more tie- dyed clothes than you've seen since around 1969 and enough personnel and paraphernalia (licit and illicit) for a miniature Woodstock. The Grateful Dead, a group that is 20 years old this year, was making a two-night stand at the Merriweather Post Pavilion. But long before it got there, its army of followers was assembling in the parking lots and fields and carefully tended forests nearby.

People gathered early in the day for the night's show, hanging out in tents, cars and spray-painted rattletrap vans. Many were too young to remember the era in whose honor they had dressed and decorated themselves. Their hair was too neatly trimmed and they were wearing Nikes. Like the movies of the 1960s and '70s that tried to portray the young of that time, they couldn't quite get it right.

Also there, however, were some of the old and legendary breed of the '60s -- long in the tooth and thick in the middle, and in some cases appearing pretty ravaged and fogged up. Steadfast devotion to the excesses of one's youth can be wearing. Many looked as if they had been following the ever- touring Grateful Dead for all of its 20 years and would still be doing so when the famous group played its first concert on Mars.

The Grateful Dead is an organization that takes music seriously. When the group learned that two of its concerts conflicted with its tickets for performances of Wagner's operas in San Francisco, it canceled the concerts. It has never made any silly, pretentious rock videos -- which is to say it has not made any videos at all -- nor has it released a record album in five years. The group just does concerts, which, according to the critics of such music, is what it does best. One of its chief rewards is to be followed up and down the coasts and across the heartland by merry caravans in search of the year 1965.