Maps and spatial data for STL are not kept on conserve online, but in The Nature Conservancy's (TNC) Map Gallery.
GIS Spatial data can be found here.

Links to STL Maps

STL Aquatic Portfolio Sites , PDF Version
STL Aquatic Systems , PDF Version
STL Ecoregional Portfolio , PDF Version
STL Bedrock Geology , PDF Version
STL Bedrock Geology in the US Portion Only , PDF Version
STL ELU Groups for Candidate Matrix Blocks , PDF Version
STL Ecological Land Units (ELU) , PDF Version
STL Ecological Land Units (ELU) in the US Portion Only , PDF Version
STL Elevation Map, PDF Version
STL Landcover, PDF Version
STL Managed Areas
STL Matrix Blocks
STL Road-Defined Blocks, PDF Version