At 6 p.m. on a Tuesday, the 10 bar seats at Portland Pie Company in Westbrook were taken. Three flat-screen TVs were on silent but airing the U.S. Open on one and the Red Sox vs. Tigers game on the other two.

One hundred or so beer mugs were dangling above patrons’ heads (a few people were drinking from their “mug club” mug), and at the end of one of the tennis matches, an older gentleman got up to leave but first stopped at a family’s table to jokingly pull a quarter out of a young girl’s ear.

This is the nightly scene at the Westbrook location of what has become a fast-growing pizza chain in Maine and New England. Since 1997, Portland Pie has expanded from its single location in Portland to six, with Scarborough and Westbrook; Manchester and Nashua, N.H.; and Reading, Mass.

The chain is giving other local pizza enterprises like Otto a run for their money. Otto currently has five locations but is expected to balloon to seven by the end of the summer. Still, Portland Pie will cover more territory, with locations in three states as opposed to Otto, which will have a stake in two.

So, what’s Portland Pie’s secret?

For one thing, it’s consistent with daily pizza and drink specials. There’s always a draught beer featured, often for $3 (most recently it was the Shipyard Hefeweizen), and from 3 to 5 p.m. daily, a 10-inch personal pizza is $5.99 (they usually start at $10.79).

There’s also a Shipyard Sampler for $4, which features four 4-ounce pours of Shipyard brews. And the wine flight, a generous pour of two reds and two whites, is only $8.

There’s also Maine Mead and other wines by the glass and by the bottle, and an impressive list of 18 cocktails. The Little Diamond Iced Tea (vodka, gin, rum, tequila and Pepsi) is a favorite.

Additional specials include mimosas for $3 and Bloody Marys for $5 on Saturdays and Sundays.

Each Portland Pie location offers the chain’s signature pizza dough flavors such as beer, garlic, basil and honey. There’s also a gluten-free option that’s surprisingly edible and tasty for an additional $2.50 (it’s unclear why the gluten-free dough costs substantially more). And of course, there are plenty of options for non-pizza eaters — sandwiches, salads, pasta, calzones and appetizers (lobster sliders, anyone?).

Portland Pie has figured out how to create a family-friendly and reliable sports bar pub. The pub aspect is partly due to the aforementioned mugs hanging overhead at the bar. Each white mug has a number, and belongs to a regular customer of the Westbrook location.

The “mug club,” as it’s dubbed, is kind of a no-brainer: Pay $25 a year and receive 20-ounce beers for the price of a 16-ounce pour. Each time you buy, points are applied to the PIE-er program. Once you spend $300, you get $25 back, a free meal on your birthday, and 50 percent off wine bottles Monday through Wednesday.

For this deal, it’d be shocking to find anyone in Westbrook not participating in the mug club. And by the looks of how full the bar was even on a Tuesday night, it seems Portland Pie Company has settled in just the right spot on this stretch of Main Street.

Claire Jeffers is a freelance writer.