This looks exactly like the gateway to a world of sylvan rest and rustic pleasure that it was meant to be. In passing we note that the gatehouse is actually a building, with a room on either side of the gate: we used to have staff to sit here and tend to park visitors’ needs.
The architect was a big deal for such a small structure: John Russell Pope. He had some famous commissions in Washington (that’s Big Worshington to residents of the South Hills): the Jefferson Memorial, the National Gallery of Art, Constitution Hall, and the National Archives, among other buildings. In Pittsburgh he is best known for the colossal Winter mausoleum at Allegheny Cemetery.