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I'm looking for a more detailed dataset than the 1:2,000,000 shapefile available from the National Atlas, preferably one suitable for use at 1:24,000.

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Since the continental divide is determined hydrographically, I would use data from the National Hydrography Dataset (NHD), or the analagous Watershed Boundary Dataset (WBD). Based on this geodatabase of HUC8 boundaries from WBD, the results look pretty good at 1:24,000 scale:

Continental divide This shows Triple Divide Peak in Montana.

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Just what I was looking for. I knew it was defined hydrologically, but I'm not familiar enough with the hydrology datasets to have thought to look for the boundary dataset. I'm not sure how one would extract (or show) just the continental divide, since the actual individual features are more local basins. For example, in the part of NM that I am interested in, the features defining the divide are labeled as the Rio Grande and Upper Colorado regions. How would one select just those features that contribute to the divide? –  Llaves May 3 '12 at 1:00
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The boundary regions have a hierarchical system of identification. The first two digits (HUC2) define broad basins. The first four digits (HUC4) define watersheds within those basins. And so on, all the way to HUC12, which represents extremely small catchment areas. Since the continental divide separates the broad basins (HUC2 areas) you can just Dissolve based on the HUC2 attribute, and the boundary that separates the resulting polygons is the Continental Divide. –  dmahr May 3 '12 at 2:12

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