St. Mark's congregation engaged celebrated architect Burns as he was completing a decade of outstanding Episcopal churches in Philadelphia. He designed St. Mark's in the manner of an English parish church, a type he employed in smaller towns such as Bryn Mawr (Church of the Redeemer; MO10) and Uniontown (1886, St. Peter's Episcopal Church). With an antiquarian's eye for detail and a painter's sense of color, Burns produced a richly textured and patterned surface in warm tones of brick, sandstone, and terracotta and stickwork at St. Mark's. Three Tiffany stained glass windows, including a rose window over the altar, demonstrate the role of sophisticated churches in spreading high art. The ornate main altar was the gift of the Reverend Dr. Thomas Worral, church rector from 1925 to 1935. Worral made a drawing of an altar he admired in St. Mark's Cathedral in Venice and hired English carpenters to replicate it for the Lewistown sanctuary.