The province spans a landlocked area of 1,159.0 km2 (447 sq mi), making it the sixth largest of Valaparíso Region's eight provinces. According to the 2002 census, which was conducted before the province came into law, the sum of Marga Marga's communes was 277,525 persons, making it the second most populous province in the region after Valparaíso Province. At that time, there were 267,022 people living in urban areas, 10,503 people living in rural areas, 133,605 men and 143,920 women.