White Rock is named for a distinctive large white boulder on its beach near the promenade, a glacial erratic that migrated south during the last glaciation. The 486-ton granite boulder was kept white by shellfish-eating seabirds whose guano covered the rock, so much so that 19th-century sailors used it as a beacon. However, it is now kept white through monthly applications of white paint by the city parks department, and has been a popular graffiti target for over thirty years.