A rail seat and support structure for mounting, cushioning, anchoring and insulating a rail. A flexible rail seat is provided with the rail seat being of resilient material and having surfaces assisting in forming a recess. The recess is open to the exterior of the rail seat on its upper surface and has an interior configuration corresponding to the base flange and the lower portion of the vertical portion of the rail so as to receive and engage those portions of the rail in insulating, cushioning and bearing relationship. The rail seat also has at least one interior chamber adjacent to each side of the rail and a bar in each of the chambers. A base plate having a horizontal portion and two spaced upright longitudinal side walls is present and the rail seat is positioned in the base between the side walls and is adapted to receive the rail in substantially parallel relationship with the side walls. A clamping plate is positioned on the upper surface of the rail seat on both sides of the rail and mounting means are present for fastening the assembled rail seat and support structure to a rail bed so as to maintain the rail seat and support structure in assembled arrangement, connected to the rail bed, and to retain the rail in mounted, cushioned and insulated position.