'Locoweed' may apply to several leguminous plants (Bob the postman is correct).
Oxytropis-Astragalus species (pea-legume family, flowers resemble sweet peas) are the ones that cause the most damage to livestock. There are several species, spread from Mexico to Canada, much more common in the West.
See U. S. Dept. Agriculture notice- Locoweeds

Datura ('jimsonweed'), nightshade family, is toxic but is not a locoweed. The common one in the U. S. has large white flowers and a taproot.

It would seem the food with the 'green powder' is a form of pemmican, which was widespread in use across northern U. S. and southern Canada.