Alex Steinweiss was the man who basically invented the album cover. Before him, record sets were sold in book-like albums with brown paper interior sleeves containing multiple records, and the covers were simply plain, like the old photo albums or scrapbooks.
Steinweiss convinced his bosses at Columbia records to invest in the equipment to print on these covers. They started with generic covers that would leave a space for the album titles, and then gradually each album would have it's own conceptual design, as we know it today.
For more covers and info, visit Poul Webb's blog here.