Bob Carpenter became the 42nd player in National Hockey League history to reach the 50-goal plateau tonight. Of greater significance, he is the first born in the United States.

If it was a memorable night for Carpenter, however, it was a forgettable night for the rest of the Washington Capitals. Battling back from a two-goal deficit to tie the game, they were beaten by the Montreal Canadiens, 3-2, when Scott Stevens inadvertently deflected the puck into his own net with 5:42 left in regulation time.

The victory kept Montreal, which visits Capital Centre Friday night, in a first-place Adams Division tie with Quebec. Meanwhile, the runner-up Capitals fell eight points behind Philadelphia in the Patrick Division.

Carpenter's historic goal came on a rebound of a shot by Stevens late in the second period. It was his fourth in four games and put the milestone out of the way in relatively painless fashion.

"I had to reach for the puck and I knew the goalie was sliding along the ice, so I wanted to make sure I got it high enough," Carpenter said. "I wasn't thinking about 50 at the time, but it's always in the back of your mind. At least I didn't have to wait very long. When I got to 46, there was a little break, but this was four in a row and it made it easy.

"I wasn't really worried about getting it. There were nine games left and I knew it would come sooner or later. But a couple of people asked me to project an interview, how I'd feel when I got it, and I said, 'No way.' You can always get hurt or get in a slump. There's no point in tempting fate.

"I have to thank all the guys on this team. They were great. They kidded me all the time and made jokes to keep me loose. I just hope this gives a boost to the kids in the States and gives them some incentive to stay in hockey longer."

Washington Coach Bryan Murray managed one of his few smiles of the night when he was asked about Carpenter, saying, "It's a real achievement for him and I hope now that the hurdle's over, if it was a hurdle, he'll get l0 or 12 more and have a good playoff."

The previous high by a U.S.-born player was 41 goals, set last year by Joe Mullen of St. Louis. Carpenter reached 42 in Winnipeg Feb. 13 and he said tonight, "I broke the American record in Canada, too, so I might as well get 50 here. It's special reaching 50 against this team."

In a bit of an oddity, Carpenter, from the suburbs of Boston, was reaching his milestone in Montreal; the first NHL player to score 50 in a season, Rocket Richard of Montreal, hit that figure in Boston on March 18, 1945.

Stevens was a central figure in most key plays in the game. He hooked Mats Naslund down on a foul that resulted in a penalty shot, although Naslund failed to convert it. Then Lucien DeBlois' pass bounced off his skate to Alfie Turcotte for the goal that made it 2-0. Stevens assisted on Carpenter's 50th before things turned sour.

In the third period, with the score tied, Stevens attempted a 45-footer that struck a post and caromed away. "The defenseman (Chris Chelios) was coming out and he screened the goaltender," Stevens said. "I had good feelings about that shot. Any luck and it hits the post and goes in. But I wasn't having much luck tonight."

Stevens' bad luck reached its zenith later, when he was defending against a three-on-two and Guy Carbonneau centered the puck from the left wing corner toward DeBlois at the right post. Stevens reached out to block it and the puck deflected past Pat Riggin into the Washington net.

"It was a three-on-two and I've got to stay in the middle," Stevens said. "I play it the same way every night. It was just the way the bounce went. I cut off the pass and it went off my stick into the net."

The Capitals started no better than they finished, as Bob Gainey converted DeBlois' pass from behind the Washington net after just 14 seconds. The New York Islanders had scored at the 20-second mark in the Capitals' last road game.

"We were caught flat-footed again right off the bat and for a long time we were struggling to get a shot on goal," Murray said. "After an uphill battle we get back into the hockey game, then we turn the puck over, they get a four on two and we lose it."

Referee Bob Myers awarded Naslund a penalty shot at 6:44, after he took Craig Ludwig's headman pass and was on a breakaway when Stevens hooked him down from behind. On the penalty shot itself, Naslund was embarrassed, never getting a shot off. As he deked Riggin, moving the puck from backhand to forehand, it hopped over his stick and skidded away.

"I saw him come out and I wanted to get it high," Naslund said. "But the puck jumped over my stick and that was it. It's the second time in my career; at least I got a shot away before."

Naslund was foiled by the Islanders' Bill Smith on a penalty shot in a key episode of last year's Prince of Wales Conference playoffs. Riggin, winless in six starts in March, had been beaten on his last two penalty shots, by Michel Goulet of Quebec and Dave Hannan of Pittsburgh.

Turcotte's goal, off DeBlois' deflected pass, made it 2-0. Naslund struck a post early in the second period, while it was taking Washington more than seven minutes to try a shot at goalie Steve Penney.

Carpenter's goal brought the Capitals to life and, 2 1/2 minutes later, he took the puck away from Larry Robinson and set up Mike Gartner in front for his 45th goal.

Now the pressure of the fight for 50 falls on Gartner's shoulders.