Right now I load "StreetMap North America.mxd" from ESRI Data Maps 10 for use with arcobjects / arcengine 10 in Visual Studio with C#. Since it's slow I am looking for a way to turn off all data except for data from Minnesota and Wisconsin. What are the main steps to accomplish this?
For each layer that has a State field, I'd check to see if it has an index, and if not then add an index using ArcCatalog (or IFeatureClass.AddIndex if you don't). After that I would apply a feature layer query definition to each of those layers that filters out only the two states with ArcMap (or with IFeatureLayerDefinition.DefinitionExpression if you don't have arcmap). After doing this, only features satisfying the definition expression will draw.