A method of making a pre-fabricated insulated wall structure comprising: (a) placing a frame having a front frame surface and a foam panel attached to the front frame surface on a track conveyor configured to convey the frame in a substantially upright position in which the frame lies on rotating members of a substantially vertically positioned track and the foam panel lies on rotating members of a lower substantially horizontally positioned track, wherein (i) the frame comprises a first member, a second member spaced apart from the first member; and connecting members extending between the first member and the second member, (ii) the first member, the second member, and the connecting members each comprise a front surface and a rear surface that form the front frame surface and a rear frame surface, and (iii) the foam panel, the first member, the second member, and the connecting members define a cavity within the frame; (b) conveying the frame having the foam panel attached thereto on the track conveyor in a substantially upright position to a spray foam application station; and (c) spray applying a spray foam composition into the cavity of the substantially upright positioned frame having the foam panel attached thereto in the spray foam application station to form a substantially upright positioned pre-fabricated insulated wall structure having a foam layer deposited in the cavity in which the foam layer adheres to the foam panel, wherein the track conveyor comprises: a plurality of spaced apart racks, wherein the racks have an A-framed construction comprising legs (252, 254) and an elevated cross-member extending between the legs (252, 254) and attached thereto, wherein the racks comprise a rigid flap extending outwardly from a leg and upon which the frame having the foam panel attached thereto rests while on the track conveyor; an upper substantially horizontally positioned track mounted on the racks and extending therebetween and comprising rotating members disposed along the length of the track; the lower substantially horizontally positioned track mounted on the racks and extending therebetween and comprising rotating members disposed along the length of the track; and the substantially vertically positioned track mounted on the rigid flap of the racks and extending therebetween and comprising rotating members disposed along the length of the track, wherein the substantially vertically positioned track is disposed beneath the lower substantially horizontally positioned track, wherein the tracks can comprise any of a variety of devices to facilitate conveyance of a wall structure along the track(s) in a substantially upright position. (a) placing a frame having a front frame surface and a foam panel attached to the front frame surface on a track conveyor configured to convey the frame in a substantially upright position in which the frame lies on rotating members of a substantially vertically positioned track and the foam panel lies on rotating members of a lower substantially horizontally positioned track, wherein (i) the frame comprises a first member, a second member spaced apart from the first member; and connecting members extending between the first member and the second member, (ii) the first member, the second member, and the connecting members each comprise a front surface and a rear surface that form the front frame surface and a rear frame surface, and (iii) the foam panel, the first member, the second member, and the connecting members define a cavity within the frame; (i) the frame comprises a first member, a second member spaced apart from the first member; and connecting members extending between the first member and the second member, (ii) the first member, the second member, and the connecting members each comprise a front surface and a rear surface that form the front frame surface and a rear frame surface, and (iii) the foam panel, the first member, the second member, and the connecting members define a cavity within the frame; (b) conveying the frame having the foam panel attached thereto on the track conveyor in a substantially upright position to a spray foam application station; and (c) spray applying a spray foam composition into the cavity of the substantially upright positioned frame having the foam panel attached thereto in the spray foam application station to form a substantially upright positioned pre-fabricated insulated wall structure having a foam layer deposited in the cavity in which the foam layer adheres to the foam panel, a plurality of spaced apart racks, wherein the racks have an A-framed construction comprising legs (252, 254) and an elevated cross-member extending between the legs (252, 254) and attached thereto, wherein the racks comprise a rigid flap extending outwardly from a leg and upon which the frame having the foam panel attached thereto rests while on the track conveyor; an upper substantially horizontally positioned track mounted on the racks and extending therebetween and comprising rotating members disposed along the length of the track; the lower substantially horizontally positioned track mounted on the racks and extending therebetween and comprising rotating members disposed along the length of the track; and the substantially vertically positioned track mounted on the rigid flap of the racks and extending therebetween and comprising rotating members disposed along the length of the track, wherein the substantially vertically positioned track is disposed beneath the lower substantially horizontally positioned track,