The league is the Philadelphia area's best collection of basketball players. Lowry played with former NBA player Sean Singletary and against former NBA player Mardy Collins - pros Hakim Warrick, John Salmons, and Lavoy Allen also are expected.
It's also one of its most accessible leagues.
League director Kevin Towns estimated that 400 or 500 people came to watch Wednesday - but at times, it seemed as if the waves of players who arrived each hour outnumbered spectators. Alongside two courts, the bleachers were pulled out two rows deep. On the third, a few folding chairs dotted the perimeter. Admission was free.
"On any single night, you can play against a guy that plays in Division III, Division II, plays overseas, Division I, NBA. On any single night," Towns said. "So where else can you go and get that?"
And even that may not be the league's best perk.
"It's air-conditioned," Towns said. "It's like the Taj Mahal of basketball."
Most major basketball cities have their own summer leagues: The NCAA certified 67 others for the summer of 2013. Philadelphia, though, is distinctly situated. Most cities don't have the size and talent of Philadelphia. Those that do don't have the schools to keep the players local.
In Philadelphia, most of the players who grow up here stay here. And in the offseason, all these players, and the professionals who return home for the summer, need a place to play.
Yet for a while there was none. Amateurs would play in the Sonny Hill or Hank Gathers League. For the professionals, John Hardnett would organize competition in the offseason. When Hardnett died in 2010, those opportunities mostly disappeared.
That, Collins said, made it "hard to get a good run throughout the city."
Then in 2008, Jameer Nelson and Delonte West added star power to the Delco League. In recent years, Collins' team dueled with Salmons' and word spread. Now, Towns estimates, more than 75 percent of the league consists of Hardnett's former players.
This year, the league has 24 teams that play in three one-hour sessions, on three courts, several times each week. The professionals play against other professionals, but some of the collegiate teams also get a chance.
"If you're a pro guy," Collins said, "they're not just going to let you have it every night."
Wednesday's opening game was a matchup of the last two league champions. The clock malfunctioned more than once, and plenty of points were scored in 44 minutes of running clock play. Collins' team won in overtime, 101-100, on a late three-pointer.
Lowry's desperation heave went in, but the handful of people watching knew it was after the buzzer. And they knew they had just watched a rare Philadelphia summer basketball treat.
Contact Zach Helfand at firstname.lastname@example.org. Follow on Twitter @zhelfand.
For information on the Delaware County Pro-Am League, go to www.delcoproam.com.