A multi-layer wall panel includes a core filler material surrounded by two plastic sheets. Each sheet includes three-dimensional texture formed to resemble masonry or other desired aesthetics. A layer of concrete may be disposed between each sheet and the filler material. The sheet may be removed from the concrete layers to expose the concrete surfaces. Multiple wall panels may be stacked on top of one another and joined side-by-side with posts and connectors to form a wall assembly. A method for manufacturing vertical concrete wall structures is also provided.