First Legislative District of Rizal is the country’s most populous

Section 5 (3) Article VI of the 1987 Philippine Constitution stipulates that each  province (regardless of population size) and each city, with a population of at least  250,000 persons, should have at least one Representative in the Congress. As of  31 August 2021, the Philippines had a total of 253 legislative districts (LDs).

Among all the legislative districts, the First LD of Rizal was the biggest in terms  of population size, with 1.21 million persons based on the 2020 Census of  Population and Housing (2020 CPH). It was followed by the First LD of the City of  Caloocan in the National Capital Region (NCR) with 952 thousand persons, and  the First LD of Maguindanao with 926 thousand persons. The rest of the ten most  populous LDs had a population of more than 750,000 persons. (Tables A and 1)

Moreover, 58 other LDs posted a population of more than 500,000 persons.  (Table 1)

Lone LD of Batanes is the least populous LD

The Lone LD of the island province of Batanes was the least populous with 18,831 persons, followed by the Lone LD of two other island-provinces – Camiguin  with 92,808 persons and Siquijor with 103,395 persons. Except for the Lone LD of  the City of San Juan in NCR, First LD of Surigao del Norte, First LD of the City of  Marikina in NCR, and First LD of Masbate, the rest of the ten least populous LDs  are small provinces composed of only one LD – the landlocked provinces of Apayao  and Mountain Province and the island province of Dinagat Islands. (Tables B and 1)