According to the 2002 census of the National Statistics Institute, Constitución spans an area of 1,343.6 km2 (519 sq mi) and has 46,081 inhabitants (23,389 men and 22,692 women). Of these, 37,202 (80.7%) lived in urban areas and 8,879 (19.3%) in rural areas. The population grew by 14.2% (5,741 persons) between the 1992 and 2002 censuses.
After the devastating 8.8 magnitude earthquake that struck Chile on 27 February 2010, an estimated 350 people died in Constitución from a tsunami. Two weeks before the earthquake, the local people were trained to head for the hills if unable to stand during the tremor, as the likelihood of a tsunami was high. The tsunami was estimated to be 15 m (49 ft) high.
Pedro Muñoz, a fisherman, with his skiff, rescued celebrants of the end of summer from an island on the Maule River, making two trips between the island and the riverbank, before being swamped and killed by the third tsunami wave, on his third trip.
Constitución was damaged by the earthquake and subsequent tsunami. Restoring power in the city in the immediate aftermath was impossible because of damage from the tsunami.