Abstract: A tower crane is carried on a platform rotatably mounted on a large ring with the tower pivotally mounted on the forward portion of the platform above the ring and a mast mounted on the platform adjacent the boom and extending upwardly and rearwardly therefrom. A counterweight support at the rear end of the platform also rides on the ring and is connected to the top of the mast by a backstay. At the top of the tower is a pivotally mounted, forwardly projecting boom and an upwardly and rearwardly inclined boom strut whose upper end is pin-connected to the top of the mast by a backstay strut. A tower backstay is connected to an upper part of the tower and extends generally horizontally rearwardly to the top of the mast where it is also pin-connected. By removing the pin-connections at the top of the mast, the tower, boom, boom strut, backstay strut and tower backstay can be pivotally raised and lowered as a unit by powered erection rigging mounted on the platform.