This map shows all the major streams in the USA at 1:1,000,000 scale. Other waterbodies (e.g., lakes) are not shown, but were used by the USGS in the calculation of the Strahler stream order.

For those unfamiliar with Strahler number, it is a mathematical concept commonly used in hydrology as a method for classifying a stream’s size based on the hierarchy of tributaries feeding into a given segment. Larger numbers generally correspond to larger streams.

For an example, see this image.

Data source: http://www.nationalatlas.gov/atlasftp.html?openChapters=chpbio%2Cchpwater#chpwater