The 49th state Wednesday night got its first professional theater, a striking step for the regional theater movement which has become such a force in "the lower 48."

The play is "Scapino," on adaptation of Moliere's "Scapin," originally produced by England's Bristol Young Vic, with a strong dash of Italy's Commedia dell'arte. The version by director Frank Dunlop and actor Jim Dale was popular in New York three seasons ago, though its national tour missed Washington.

With Curt Dawson (who once played "Sleuth" at the National in the title part, the broadly funny farce seems an ideal choice to attract audiences here. The sold-out first night audience clearly relished this tale of a rascal in modern Naples, a colorful sport replete with Coca-Cola bottles, a Wurlitzer jukebox and scuba diving fins. Staged by Robert J. Farley, the production is worthy of the professional best.

Not that Alaska has not had theater. There are amateur drama groups in the most surprising spots of this largest American state. Individual professional performers have visited since gold-rush days, but logistics in reaching the state's population of just over 400,000, in an area 1,500 miles north of Seattle posed obvious barriers.

The producing organization is ARC, the Alaska Repertory Company, begun two years ago by the Alaska State Council on the Arts. Paul V. Brown, an eight-year Alaskan originally from New York, is producing director. Farley has served with the APA-Phoenix McCarter Theater, Princeton, N.J., the Atlanta Arts Center, Ga., and NBC-TV Hollywood.

Most of the players have appeared in major roles from New York and Chicago to Los Angeles and San Francisco.Several leads are Alaskans as are six interns under PTP, the Professional Training Program. This is definitely to the satisfaction of Alaska theater folk, who have feared being frozen out with the arrival of professionals from the "outside."

There's not a poor performance in the lot, including those by Dorothy Hill. Ryal White, Michael Hureaux and James Hotchkiss, the Alaska resident. Especially noteworthy are the voices well projected in diction and nuances.

"Scapino" will run for two weeks, to be followed by Noel Coward's "Private Lives," to be staged by Lee H. Salisbury, whose University of Alaska productions at Fairbanks have commanded admiration down the Pacific coast. Its two-week run will be followed by David Rintels' one-man drama, "Clarence Darrow," which Henry Fonda introduced in Washington. Philip P. Pleasants, excellent as Geronte in "Scapino," will have the Darrow role and will tour the States after the Anchorage run.

ARC's beginnings in some ways are like those of Arena Stage Movers and shakers have rallied behind Brown much the way Arena's earliest supporters did the Fichandlers.

About half of Alaskas' population lives in Anchorage. Can only 200,000 support a theater? How is this state theater going to serve the incredibly vast reaches of the state's 586,000 square miles?How are the small pockets of the population to be reached?

Fairbanks, the second largest city, was founded in 1902 and has the largest campus and considerable amateur activity. But its population of 40,000 could not support even so modest a program as Anchorage plans. Dating from 1880, Juneau, the present capital, has but 30,000 as the third city. Going back only to 1915, bustling, thriving Anchorage is viewed by the others as a latecomer, rather the way San Franciscans view Los Angeles.

So the organization, its volunteers and professional staff face a challenging situation. Fortunately, "Scapino" is a fine start and merits full houses for the 620-seat Sydney Laurence Auditorium.