PIP: Statistical data available on the 19th century Mexican population are for the most part scarce, of doubtful reliability, and dispersed. The war of independence, civil wars, regional conflicts and foreign interventions affected demographic behavior and also hampered implementation of a national census. The 3 types of available data on the 19th century population include a few state censuses, some censuses conducted by individuals, and data from civil registration and parish records. This work examines general development of Mexico's population in the 19th century, regional distribution, and political divisions. Mexico's population is estimated to have increased from 6,837,100 in 1803 to 10,448,000 in 1884, figures indicating a slow rate of growth. The relatively slow growth is probably explained by higher mortality rates not compensated by the high fertility. Mortality began to decline around 1850, and overall growth rates increased towards the end of the century. Epidemics, pandemics, poor harvests, droughts, and civil wars all contributed to the high rates. Colonial and prehispanic patterns of population distribution remained almost unchanged until midcentury, when a significant movement toward the north began to occur. Available sources do not permit division of Mexico into regions based on socioeconomic data or on economic structures. Juridicopolitical divisions offer useful approximations for regional analysis of population trends. Among 5 resulting regions, the North Pacific contained slightly over 3% of the population and was largely isolated from the rest of Mexico. The North, including Sonora, Chihuahua, Coahuila, Durango, Nuevo Leon and Zacatecas, contained around 9%. Taken as a whole, the population of the North region did not change much, but individual areas such as Sonora lost population while Nuevo Leon had an annual growth rate averaging 1.65%. The Caribbean Coast overall lost population despite some areas of growth. The share declined from 19.4% in 1825 to 10.7% in 1875. Central Mexico contained over 60% of the national population. The Southern Pacific region of Oaxaca, Chiapas, and Guerrero doubled its population between 1825-75. Its share of the national total increased from 10.11% in 1825 to 14.75% in 1875. Analysis of the development of individual states shows that there was considerable diversity tied to cultural, political, and economic factors.