Abstract: Encased innerspring mattress and cover device is assembled by positioning mattress and cover component layers, one atop the other, in sequential order, (namely mattress cover bottom, bottom panel, filling material, insulator, innerspring, insulator, filling material, top panel, and mattress cover top, respectively). Continuous zipper at perimeter of mattress cover allows mattress cover to be completely assembled prior to its attachment to the innerspring mattress interior components. Entire mattress and cover assembly can be manufactured from the bottom up without overturning any interior components of the device during its assembly.