There are different types of Larkspur and I am struggling to classify this particular variety. It looks a lot like the “Spring Larkspur” picture found in the Audubon Field Guide. Online resources are contradictory.
Delphinium is a genus of about 300 species of perennial flowering plants in the family Ranunculaceae, native throughout the Northern Hemisphere and also on the high mountains of tropical Africa.
All members of the Delphinium genus are toxic to humans and livestock. The common name “larkspur” is shared between perennial Delphinium species and annual species of the genus Consolida. Molecular data show that Consolida, as well as another segregate genus, Aconitella, are both embedded in Delphinium. The name “delphinium” derives from the Latin for “dolphin”, referring to the shape of the nectary. — Wikipedia
The Audubon Field Guide puts “Spring Larkspur” in the Buttercup family. (Delphinium Tricorne).