Walnut Grove is a city in Greene County, Missouri, United States. The population was 652 at the 2020 census. It is part of the Springfield, M…Walnut Grove is a city in Greene County, Missouri, United States. The population was 652 at the 2020 census. It is part of the Springfield, Missouri Metropolitan Statistical Area. Claudette Riley of the Springfield News-Leader described it as "a largely agricultural community with a relatively low tax base."