The Multi-angle Imaging SpectroRadiometer (MISR) is in its ninth year of operation aboard NASA's Terra satellite. MISR acquires imagery at nine view angles between 70.5º forward and backward of nadir. Stereoscopic image matching of red band data at 275-m horizontal spatial resolution provides measurements of aerosol plume heights in the vicinity and downwind of wildfires. We are supplementing MISR's standard stereo product with more detailed, higher vertical spatial resolution stereo retrievals over individual smoke plumes, using the MISR INteractive eXplorer (MINX) analysis tool. To limit the amount of data that must be processed, MODIS (Moderate resolution Imaging Spectroradiometer) thermal anomaly data are used to identify fire locations. Data over North America are being analyzed to generate a climatology of smoke injection heights and to derive a general parameterization for the injection heights that can be used within non-plume-resolving chemical transport models. In 2002, we find that up to about 30% of fire plumes over North America reached the free troposphere. Sufficiently buoyant plumes tend to become trapped near stratified stable layers within the atmospheric vertical profile, supporting a result first obtained on a more limited set of MISR data [1]. Data from other years are being processed to further establish the robustness of these conclusions.