Here are some links for viewing aerial photos on interactive maps:
http://www.lmic.state.mn.us/chouse/northstarmapper.html
State of MN, 1991 and 2003 photos, USGS Topo Maps

http://get.live.com/local/overview
http://earth.google.com/
http://terraserver.homeadvisor.msn.com/default.aspx

1938 photos can be downloaded in jpeg format from DNR at the following site:
http://www.dnr.state.mn.us/maps/landview.html  an interactive map for selecting historic photos by location
(1930's only, in Stearns), and viewing 1991-92 USGS DOQ or USGS Topographic Map (DRG)

GIS Data Links:
http://www.lmic.state.mn.us/chouse/index.html    Land Management Information Center with Links to other agencies.
http://deli.dnr.state.mn.us/index.html    DNR Data Deli
http://datagateway.nrcs.usda.gov/GatewayHome.html   USDA NRCS Geospatial Data Gateway
http://soildatamart.nrcs.usda.gov/Default.aspx   USDA NRCS Soils

Interactive Soil Survey Map
http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx