PORTSMOUTH — When The Black Dog held its grand opening Saturday, a lot of people came to check it out, many bringing black dogs of their own, which were welcomed by the staff.

A big black dog mascot, donned by Andrew Trout, welcomed people to the store. When he is not playing a black dog, Trout is a sales associate for the store.

The Portsmouth location is the 28th Black Dog store. Manager Bernadette Curran said the company was started in 1971 by Capt. Robert Douglass, who opened The Black Dog tavern on Martha’s Vineyard. The retail apparel and dog locations soon followed.

“When he opened a tavern, the waitstaff wore these Black Dog T-shirts. People wanted to buy them, sometimes offering to buy them from the wait staff,” Curran said. “They weren’t offered for sale and that’s how the brand was born.”