The Anaconda Smelter Stack is a brick smoke stack, once part of the smelter of the Anaconda Copper Mining Company at Anaconda, Montana in the United States. The stack is 585ft tall, excluding its foundation. The stack contains 2,464,652 locally manufactured perforated tile bricks, each averaging 2.7 times larger by volume than the size of a normal brick. The lowest 80ft is octagonal in cross section while the rest is circular. The vertices of the octagon point to the cardinal and intercardinal directions, north, northeast, east, etc., while its sides face the secondary-intercardinal directions, north-northeast, east-northeast, etc. Two large rectangular openings are in the octagonal portion, both slightly smaller than a side, on the east-southeast and south-southwest sides. Its circular portion is encircled by many large steel rods for reinforcement. The concrete foundation is stated to be 30ft tall, but that is its maximum height on its south-southeast side (it is much shorter on the opposite side). The inside diameter of the stack is 75ft at the bottom and 60ft at the top. The wall thickness ranges from six feet at the bottom to two feet at the top.After the concrete foundation was completed in May 1918, construction of the stack began on and was completed on. It was built by the Alphons Custodis Chimney Construction Company of New York. At the time it was built, it was the tallest masonry, brickwork structure and chimney of any kind in the world and it remains the world's tallest and possibly largest free-standing masonry structure. The Washington Monument would easily fit inside. It is commonly referred to as 'The Stack' and is a well-known landmark in western Montana.