Sitting all by itself by the side of the road on Route 24 in Flanders, about 4 miles from Riverhead, the pure white bird — with its orange bill and bright red eyes made from Model-T taillights — makes the Big Duck look like a simple child’s drawing come to life. The only giveaway that something else is afoot is the dark outline of a door just beneath the duck’s throat.

The 20-foot-high, 30-foot-long Big Duck was built in 1931 by an ambitious duck-raising farmer who hoped to attract more customers and was inspired after a stop at a coffeepot-shaped coffee shop during a trip through California. Ducks were big business on Long Island at that time; in 1939 there were 90 duck farms in Quogue alone.

Ducks and eggs were sold from a shop within the building, seen as a model for large scale advertisement-building across the country. So influential was this particular Peking poultry that the term “duck” is still used in architecture whenever a building is made into a literal translation of an object.

Today the Big Duck is a National Historic Landmark with a shop run by Friends for Long Island’s Heritage, a nonprofit group working to preserve Long Island’s past. On sale are lots of duck collectibles — duck books, duck T-shirts, duck coffee mugs, and the like — along with postcards and books.