With the Detroit Pistons playing their final game in the building that saw them win three NBA championships, Beal scored 33 points in 33 minutes to lead the Washington Wizards to a 105-101 victory.
"We knew this was a historic night, because they've had so many great teams here," he said. "We knew they wanted to have a party, and we decided to try to ruin it."
Markieff Morris added 20 points for the Wizards, while Tobias Harris led the Pistons with 22.
The highlight of the night for Detroit fans was a halftime ceremony that honored the top players from the championship teams, with Isiah Thomas and Dennis Rodman posing for pictures with Ben Wallace and Chauncey Billups.
Washington rested John Wall and Otto Porter Jr. in preparation for the postseason, but Scott Brooks brought his starters back to try to close out a tight game.
"They wanted to go back in and win the game," he said. "I planned to keep Brad around 30 minutes, and I probably played him a few too many, but they wanted to finish it off."
The Pistons tied the game early in the fourth quarter, but Stan Van Gundy decided not to match Brooks bringing back in his top players.
"I thought the guys we had on the floor were bringing good energy, and we hadn't gotten that from the starters," he said. "It was a tough situation for them, but they were playing hard."
With Andre Drummond, Kentavious Caldwell-Pope and Marcus Morris on the bench, Beal beat Stanley Johnson for back-to-back layups to make it 94-88 with 4:09 left.
The Pistons got within one with 1:14 left, but Markieff Morris hit a jumper and Harris missed a tying 3-pointer. Beal then iced the game with a dunk in traffic and three free throws.
"I didn't think Coach was going to put us back in at first, but he did," Beal said. "I thought we were going to be able to take advantage of the matchups and we were able to do that."
Detroit looked lackluster in the first half, especially compared to the constant video tributes to the championship teams from 1989, 1990 and 2004. Washington led by as many as 15 points and shot 51 percent for the half, while holding Detroit to 38 percent.
"The whole game was the first quarter, and we've had that all year," Van Gundy said. "People just come out and jump on us. There's only one game left, but it is something to look at for next season, because we've used the same six or seven guys all season and it hasn't been good for us."
Van Gundy went to a 3-point-based offense in the third quarter, and it helped the Pistons narrow the gap to 79-73 going into the final 12 minutes. Two more threes, the second by Reggie Bullock, tied the game at 79 early in the fourth.
"Tonight was a good sign for our young guys that are returning next season," Drummond said. "They've been playing great in the past three or four games they've been on the floor."
Washington: Beal had 18 points in the first half and was a plus-18, while Kelly Oubre, Jr. was a plus-16.
Detroit: The Pistons were 14-13 and ranked second in the league on defense before a 122-108 loss in Washington that started a five-game losing streak. Detroit never got back above .500.
With Little Caesars Arena opening in the fall, Detroit sports fans said goodbye to two historic buildings in two nights. Sunday marked the last game at Joe Louis Arena, where the Red Wings won four Stanley Cups, while Monday ended the Pistons' tenure at the Palace. The WNBA's Shock, now the Dallas Wings, won titles in both buildings.
JENNINGS REMEMBERS THE PALACE
Wizards point guard Brandon Jennings didn't have a long Pistons career - playing for them from 2013-14 until he was traded during the 2015-16 season - but said that he has fond memories of his two-plus seasons at the Palace. "My second year here was Stan's first, and we were 5-23 at Christmas and everyone wrote the franchise off," he said. "Then we went on a (12-3) streak before I got hurt, and that was really what turned the team around. I'm proud of that."
Washington: Visit the Miami Heat to end the regular season.
Detroit: Visit the Orlando Magic to end the season.