About 150 people celebrated the Church of the Covenant’s designation as a national historic landmark on Sunday with a reception and a potluck of vegetarian appetizers, the church’s pastor said.

The Newbury Street church, built between 1865 and 1867, is best known for its 42 stained-glass windows created by artist and designer Louis Comfort ­Tiffany in 1894. The collection is the largest intact Tiffany ­ecclesiastical design still in its original location in the country, according to the National Park Service, which granted the landmark designation.