Maps to add (All of these can be found elsewhere online):

1800 Township Boundaries

1804 Township Boundaries

1850 Township Boundaries

1858 (With landowners)

1876 Western PA Railroad Map (shows the 2 proposed railroads to pass through Cranberry)

1892 Depreciation Lands Map

1941 Butler County

1959 Butler County

Penn Pilot Aerial Project - would like to create some high-resolution tiles and have them in a clickable arrangement

PA County formation and evolution slideshow - 80 or so slides