California is closing a large stretch of Interstate 5 near Camp Pendleton today after the Marine Corps confirmed it would be conducting an artillery live-fire event over the freeway.

The state announced the four-hour closure Saturday morning, citing “extreme life safety risk and distraction to drivers, including sudden unexpected and loud explosions,” from the Marine Corps’ event today as part of its 250th birthday celebration. The closure will be in effect between Harbor Drive in Oceanside to Basilone Road near San Onofre and comes only three days after the Marine Corps said that no freeway closure would be necessary. 

“Due to an event at Camp Pendleton today, October 18th, Interstate 5 will be closed from Harbor Drive to Basilone Road between 11:00 am and 3:00 pm.,” California Highway Patrol said in a statement posted to its social media pages. “Drivers should expect delays on Interstate 5 and other state routes throughout Southern California before, during, and after the event.”

Electronic messages warning about the closure due to live weapon fire were visible along Interstate 5 in Los Angeles County.

In a release about the celebration on Wednesday, Oct. 15, I Marine Expeditionary Force, based out of Camp Pendleton, said that “All training events will occur on approved training ranges and comport with established safety protocols. No public highways or transportation routes will be closed.”

However, California Gov. Gavin Newsom said that the state was notified by the Marine Corps asking for CalTrans to set up signs along the freeway warning “Overhead fire in progress.” That was only a day after the Marine Corps said that artillery would be fired at its regular training ranges, Newsom said.

“Firing live rounds over a busy highway isn’t just wrong — it’s dangerous,” Newsom said. California Highway Patrol told Task & Purpose that there was no intent to close the freeway until late last night. A spokesperson for I Marine Expeditionary Force said that the Marine Corps did not request the closure of the freeway.

The artillery exercise is set for 1:30 p.m. Pacific Time. The event will feature live fire from M777 Howitzers “firing 155mm high explosive rounds from west of I-5 into designated ranges east of the interstate with all safety precautions in place,” Marines said in a statement to Task & Purpose.

The I-5 Freeway runs along the California coast between Dana Point and San Diego, passing by Camp Pendleton. The state said earlier this week that more than 80,000 people pass through that area on the freeway daily. On Thursday, Amtrak announced its Pacific Surfliner train service along the coast near Camp Pendleton would be paused due to the event. 

The event, “Sea to Shore — A Review of Amphibious Strength,” will be held at the base, including at Red Beach, and the “capabilities demonstration will feature integrated Navy and Marine Corps operations across air, land, and sea,” I Marine Expeditionary Force said on Oct. 15. Vice President J.D. Vance, a Marine veteran, and Secretary of Defense Pete Hegseth are set to attend. 

I Marine Expeditionary Force said that “[a]ll air, surface, and ground movements are scripted and rehearsed in accordance with standard operating procedures and established safety checklists.”

Update: 10/18/2025; This story has been updated with additional comments from I Marine Expeditionary Force.

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