At first I was thinking that this must be giant hogweed - but there was so much of it that I decided it must not be, as that is considered to be a noxious invasive weed here in Washington and, I think, many counties require you to eradicate it if it is found on your property.
''Heracleum maximum'', cow parsnip is the only member of the genus ''Heracleum'' native to North America. Its classification has caused some difficulty, with recent authoritative sources referring to it variously as ''Heracleum maximum'' or ''Heracleum lanatum '', as ''H. linatum'', or as either a subspecies, ''H. sphondylium'' subsp. ''montanum'', or a variety, ''H. sphondylium'' var. ''linatum'', of the common hogweed . The classification given here follows ITIS.