Sanborn Maps - Mosaic

Historic maps can be really beautiful! Beyond the nostalgic pirate map characteristics of aged paper, hand written annotations, odd nomenclature and unique surveying methods these maps offer a glimpse of how the land use, ownership and physical characteristics have changed over time. Since many of these historic relics live in library archives often bounded in hand sewn books, it is a delicate and tedious process to collect, scan and piece together each page (represented as tiles) to make one complete map.

After georeferencing all of those tiles you may get what looks like a stack of cards scattered on your basemap like I did recently whilst working with 1908 Sanborn maps:

Not to worry! You've already done the hard work. To get rid of the white space just open the layer properties and enter the magic back ground RGB 255, 255, 255 and click apply and you will be set to start caching and publishing your tiles for a stellar storymap.