[3] The district consists of Cagayan's former capital, Lal-lo, and adjacent municipalities of Alcala, Aparri, Baggao, Buguey, Camalaniugan, Gattaran, Gonzaga, Santa Ana and Santa Teresita.

It is currently represented in the 19th Congress by Ramon C. Nolasco Jr. of the Lakas–CMD.

[4][5] Prior to its second dissolution in 1972, the first district consisted of eastern and northern Cagayan municipalities of Alcala, Amulung, Aparri, Baggao, Ballesteros, Calayan, Camalaniugan, Gattaran, Gonzaga, Iguig, Lal-lo, Peñablanca, Santa Ana, Santa Teresita, and Tuguegarao, the provincial capital.

The province of Batanes was also part of the district from 1907 to 1909 as Cagayan's sub-province.

Following the restoration of the Congress in 1987, the district was reapportioned to its current composition.