Interstate A3

Interstate A3


Road map of I-A3 in Alaska

Interstate A3 follows Alaska State Route 1 (Sterling Highway) south from I-A1 (5th/6th Streets) east of Downtown Alaska to Kenai Spur Highway in Soldotna. The route initially follows the couplet of Gambell Street south 1.11 miles and Ingra Street north 1.09 miles. Sterling Highway commences south from the couplet as an eight lane arterial leading onto a freeway 8.88 miles to E 154th Avenue near Potter Marsh.

The remainder of Seward Highway south to Sterling Highway is a two lane highway with several sections of passing lanes. SR 1 straddles the east banks of Turnagain Arm to Girdwood and Portage. Hooking west across Placer River Valley, Seward Highway continues into Kenai Peninsula borough, where it gains elevation.

I-A3 and SR 1 separate from Seward Highway for Sterling Highway west at Tern Lake. Seward Highway spurs south to Seward as SR 9 while Sterling Highway leads SR 1 west to Cooper Landing and along the Kenai River to the Mystery Hills. Sterling Highway expands into a four lane boulevard  west from Sterling into Soldotna.

Route Information

  • North End – Anchorage

  • South End – Soldotna

  • Mileage – 148.12

  • Cities – Anchorage, Soldotna

  • Junctions – I-A1

Source: December 31, 2021 Interstate Route Log and Finders List

Average Annual Daily Traffic

Source: 2020 Average Annual Daily Traffic County, Alaska DOT&PF GIS Shapefile


Seward Highway south from Anchorage to Sterling was dedicated on October 19, 1951. Initially referenced as the Seward-Anchorage Highway, the 128 mile long route also connected Anchorage with Sterling Highway on the Kenai peninsula. Reconstruction continued along sections of old Seward-Hope Road between Seward and mile post 58 into 1952. The section from Girdwood to Anchorage was under contract by December 1951 for paving.1

Serving as the primary connection between the Seward Highway and Glenn Highway, Gambell Street was paved in 1960. The 1980 Anchorage, Alaska Metropolitan Area General Plan published in 1961 proposed a link between the two highways along an expanded Orca Street to the east, between Fairview and Merrill Field. However following the 1964 Good Friday Earthquake, the alignment along Orca Street was dropped from plans due to high costs. Instead city planners proposed routing traffic north along the couplet of Gambell and Ingra Streets and east via 5th/6th Avenues.2

The Alaska Department of Highways opened bids for construction of the couplet along 5th/6th Avenues between Gambell and Medfra Streets in Anchorage on March 28, 1966. The project included grading, drainage and paving along 0.42 miles of city streets.3 A low bid of $1,642,494 was submitted for construction of the Ingra-Gambell Couplet between Northern Lights Boulevard and 5th Avenue by S.S. Mullen, Inc., of Seattle. The contract let by January 12, 1966 included grading, drainage and paving along 1.648 miles of roadway along with the installation of traffic signals an street lights. The state estimated $1,466,769 for the work.4

AARoads Photo Guides

North End I-A1 – Anchorage

I-A3 Alaska Highway 1 North at I-A1

I-A3/SR 1 (Ingra St) north at I-A1 (6th Avenue) in Anchorage, AK.

SR 1 turns east onto 6th Avenue from Ingra Street northbound in Anchorage. I-A3 north ends as I-A1 begins along the continuation of SR 1 to Glenn Highway. 05/10/23

I-A3/SR 1 north at 6th Avenue east from Downtown Anchorage.

I-A1/SR 1 follow the couplet of 6th Avenue east and 5th Avenue west from I-A3/SR 1 along Ingra Street north and Gambell Street south. 05/10/23

I-A1 Alaska Highway 1 South at I-A3

SR 1 (5th Avenue) west at I-A3 (Gambell Street) in Anchorage, AK.

SR 1 becomes part of Interstate A3 south from 5th Avenue along Gambell Street east of Downtown Anchorage. 05/09/23

The south end of I-A1 and south beginning of I-A3 in Anchorage.

I-A1 ends where I-A3 south begins at the turn of SR 1 from 5th Avenue onto Gambell Street. 05/10/23

Gambell Street – South at I-A1 I-A3 Alaska Highway 1

Gambell Street south at 5th Avenue in Anchorage, AK.

Gambell Street becomes both Interstate A3 and SR 1 south at 5th Avenue. I-A3/SR 1 north follow parallel Ingra Street. 05/09/13

6th Avenue – East at I-A1 I-A3 Alaska Highway 1

6th Avenue east at Gambell Street in Anchorage, AK.

6th Avenue leads east from Downtown Anchorage to become part of Interstate A1 at I-A3/SR 1 south on Gambell Street. 05/13/23

6th Avenue east at I-A3/SR 1 south and I-A1/SR 1 north in Anchorage, AK.

I-A3 heads south from 6th Avenue in Anchorage to Seward Highway. I-A1/SR 1 east follow Glenn Highway northeast to Palmer. 05/13/23

South End Alaska State Route 1 / Kenai Spur Highway – Soldotna, Alaska

Alaska Highway 1 South at Kenai Spur Highway

I-A3/SR 1 (Sterling Hwy) south at Kenai Spur Hwy in Soldotna, AK.

Interstate A3 ends southbound along SR 1 (Sterling Highway) at Kenai Spur Highway in the city of Soldotna. 05/10/23

SR 1 continues south from the end of I-A3 in Soldotna to Homer, AK.

SR 1 (Sterling Highway) continues another 81.08 miles from I-A3 and Kenai Spur Highway to Homer. 05/10/23

Alaska Highway 1 North at Kenai Spur Highway

SR 1 (Sterling Hwy) north at the beginning of I-A3 in Soldotna, AK.

SR 1 (Sterling Highway) north becomes part of Interstate A3 at the intersection with Kenai Spur Highway in Soldotna. 05/10/23

SR 1/I-A3 north at Kenai Spur Highway in Soldotna, AK.

I-A3 underlays SR 1 north from Kenai Spur Highway to 5th/6th Avenues in Anchorage. is 05/10/23

Kenai Spur Highway at Alaska Highway 1

Kenai Spur Highway south at I-A3/SR 1 in Soldotna, AK.

Kenai Spur Highway ties into SR 1 (Sterling Highway) at the south end of Interstate A3 in Soldotna. 05/10/23

Kenai Spur Highway south at I-A3/SR 1 in Soldotna, AK.

SR 1 (Sterling Highway) travels south from I-A3 to Homer and north with the unsigned Interstate to Anchorage. 05/10/23

Kenai Spur Highway north at SR 1/I-A3 (Sterling Highway) in Soldotna, AK.

Kenai Spur Highway spurs 38.39 miles northwest from the intersection with SR 1 (Sterling Highway) and the south end of I-A3. 05/10/23


  1. “Road Commmission Reports on Activities During Past Year.” Fairbanks Daily News-Miner (AK), December 27, 1951.
  2. “Opinion: Why planners routed a highway through Anchorage’s Fairview neighborhood.” Anchorage Daily News (AK), May 25, 2023.
  3. “Calls for Bids for Anchorage City Streets.” Fairbanks Daily News-Miner (AK), March 15, 1966.
  4. “Anchorage Couplet Contract Let.” Fairbanks Daily News-Miner (AK), January 12, 1966.

Page updated September 25, 2023.