Settlement of the northern portion of Alajuela only began in earnest in the later half of the 19th century, and even so did not reach great proportions until the second half of the 20th century, owing largely to the difficult access. Much of the original colonization came from Nicaragua since numerous navigable rivers flow north from their origins in the cordilleras and empty into either Lake Nicaragua or the San Juan River. By 1850, the province had a population of approximately 15,540.