[Wikipedia] Range, Habitat, Fossilized Seeds: It is native to western North America from British Columbia to northern California, where it grows in moist to wet habitat, including vernal pools and meadows. It sometimes grows in shallow standing water such as puddles. The species is known from fossilized seeds recovered from sediments of the Pleistocene Tomales Formation and from a small paleoflora at San Bruno.[3][4] Further, Daniel Axelrod discussed Montia howellii as one of the biogeographically significant species comprising the Millerton Palaeoflora at Tomales. (link added by Mary Ann Machi)