Cagayan has 28 municipalities and one city divided into three congressional districts. It has 816 barangays. Tuguegarao City (as of December 18, 1999) is the provincial capital, regional seat, and center of business, trade, and education. It has a land area of 144.80 square kilometers and a population of 120,645 as of 2000.
The province is bounded by the Pacific Ocean on the east; on the south by Isabela province; on the west by the Cordillera Mountains; and on the north by the Balintang Channel and the Babuyan Group of Islands. About two kilometers from the northeastern tip of the province is the island of Palaui; a few kilometers to the west is Fuga Island. The Babuyan Group of Islands, which includes Calayan, Dalupiri, Camiguin, and Babuyan Claro, is about 60 nautical miles (110 km) north of Luzon mainland.
The province comprises an aggregate land area of 9,002.70 square kilometers, which constitutes three percent of the total land area of the country, making it the second largest province in the region.