It then crosses Padsan River via Gilbert Bridge and enters the city proper of Laoag, where it splits before turning to the east in front of Ilocos Norte Provincial Capitol, where the Pan-Philippine Highway commences.

At Bacarra, it bypasses the town center to the north and runs through a rural area, and then enters Pasuquin, where it serves as a major municipal street.

Between Bacarra and Burgos, it becomes a rural two-lane highway and passes through interspersed barangays along the South China Sea coastline.

N1 runs through the foothills that mark the edge of the Northern Luzon Cordillera and runs close to the coastline of Bashi Channel, where the highway zigzags through the cliffs through the Patapat Viaduct, a 630-meter (0.39 mi) viaduct that is required for the highway to pass the steep cliffs marking the northern edge of the Cordillera Range.

It then enters the province of Isabela and Nueva Vizcaya as Maharlika Highway, although it is alternatively called Cagayan Valley Road up to Guiguinto, Bulacan.

At Nueva Vizcaya, N1 runs parallel to and crosses the Magat River and traverses Dalton Pass, where Sierra Madre and Caraballo Sur meet.

Plaridel Bypass Road intersects with Doña Remedios Trinidad Highway just before approaching the poblacion of San Rafael.

It soon crosses the Bigaa River, where it passes through residential and industrial areas, and curves upon entering Bocaue, where it bypasses the town center.

There, the Asian Highway 26 concurrency returns on N1 as it turns east to follow Epifanio de los Santos Avenue (EDSA) up to Pasay.

The whole road, bypassing the capital city of Manila, is notorious for congestion which causes delays as well as economic losses in the metropolis.

At the roundabout intersection with N4 (Jose P. Laurel Highway) and Governor Carpio Avenue, it turns southeast as it leaves the province.

It then enters the province of Quezon at Tiaong, passing by the Villa Escudero plantations and going through the poblacion, followed by the municipalities of Candelaria and Sariaya and the city of Tayabas, where it turns southeast towards Lucena at the Calumpang Junction.

It enters Atimonan, where it then reaches the eastern coast of Quezon, and traverses the coastal municipalities of Plaridel, Gumaca, Lopez, and Calauag.

After traveling through kilometers of jungle, N1 enters the poblacion of Labo, Camarines Norte, where it follows local streets.

From Sipocot, N1 traverses the municipalities of Libmanan, Pamplona, San Fernando, and Milaor (where it is alternatively known as Mabolo Road) in Camarines Sur before entering the City of Naga.

At Daraga poblacion, N1 turns sharply to the west as it intersects with N630 (Rizal Avenue), which provides access to Legazpi City, and becomes a zigzag road as it leaves the province.

In the poblacion of Santa Margarita, Samar, it briefly becomes a one-way southbound road as northbound traffic is diverted to the old route along Ramon Calagos and Yangzon (Barrantes) Streets.

At its intersection with N70/AH26 (Palo–Santa Fe Road / San Salvador Street) at the vicinity of the Palo Cathedral, it then turns southeast to the towns at the eastern coast of Leyte.

At the boundary of Tagum and Carmen, Davao del Norte, the highway briefly splits into two as it crosses the Libuganon River.

The highway veers northwest at Surallah and enters Sultan Kudarat at Isulan, where it becomes Marbel-Allah Valley-Cotabato Road.

N1 enters Bangsamoro Region at Ampatuan, Maguindanao del Sur, as it crosses a river as Kakal Bridge.

At the junction of Sinsuat, Quezon, and Don Teodoro V. Juliano Avenues, N1 turns east to assume the name Cotabato–Lanao Road up to Matanog, Maguindanao del Norte; its section from the junction to Sultan Kudarat, Maguindanao del Norte is also known as Quezon Avenue.

Near barangay Crossing Simuay, Sultan Kudarat, it takes the longer, circumferential path as it meets the western terminus of N75 (Davao–Cotabato Road).

In Balabagan, it assumes the alternate name Rizal Avenue as it approaches near the coast of Lanao del Sur with Celebes Sea up to Picong, the last municipality traversed by N1 before leaving Bangsamoro.

N1 enters Lanao del Norte at Sultan Naga Dimaporo, the only municipality it passes through in Northern Mindanao.

It climbs the mountainous terrain and turns west at its intersection with N9 (Butuan–Cagayan de Oro–Iligan Road) to become alternatively known as National Highway.

Alano Street/Calle Guardia Nacional), and N971 (Wharf Road/Don Pablo Lorenzo Street), its physical continuation towards the Port of Zamboanga.