A trailer including a plurality of rearwardly-extending frame arms located on opposite sides of said main frame, each of which includes a tandem with a plurality of wheels mounted thereto; a U-shaped cross member for maintaining said main frame level from side to side; at least one length-adjustable member operatively connected to said main frame and at least one of said plurality of frame arms; selective movement of said length-adjustable member causing said distal end of at least one of said plurality of frame arms to move up or down; and an automatic leveling system for moving each said length-adjustable members and each said corresponding frame arm such that said main frame is maintained in a relatively level orientation when said trailer encounters uneven terrain.