The roughly six-month journey from Iowa to San Diego was one of the longest military marches in American history. The route took the battalion through terrain that had been crossed by few Americans, through the Sonoran Desert, through mountain passes that challenged even experienced guides. Twenty-seven members died from illness and accidents along the way.

Most of the women and children fell out of the march at Pueblo, Colorado — conditions were simply too harsh for a full family migration alongside military movement. The final contingent that arrived in San Diego on January 29, 1847 numbered 335 men and four women, under the command of Lieutenant Philip St. George Cooke. They had completed something remarkable. The problem was that by the time they arrived, there was nothing left to do.

The Mexican-American War in California was effectively over before the Mormon Battalion crossed the Colorado River. American forces had already secured the region; the military situation the battalion had been recruited to support had resolved itself without them. They arrived at San Diego not as a fighting force but as an organized labor unit looking for work.

They found it. The battalion members spent their time in San Diego engaged in construction projects that left lasting marks on the city. They built a bakery. They dug wells. They engaged in blacksmithing and cart repair. Most significantly, they built the first fired-brick structure in San Diego on the town plaza — a building originally designed as a town hall that later became the city's first courthouse. Men who had marched nearly two thousand miles to fight in a war that had already ended instead became San Diego's first significant construction force.

The historic site that commemorates the Mormon Battalion's arrival in San Diego opened in 1972 in Old Town, on the ground where the battalion encamped after its extraordinary journey. The original visitors' center was dedicated by church president Harold B. Lee; a rebuilt center opened in 2010.

The site interprets the march from the perspective of the battalion members themselves — their faith, their discipline, their relationship to the broader Mormon migration that was simultaneously pushing west toward Utah. It is a story that sits at the intersection of American military history, religious history, and the particular experience of a people trying to find safety and community in a country that had repeatedly persecuted them. The march they completed was genuinely extraordinary. The city they helped build has grown beyond anything they could have imagined.

The courthouse that the Mormon Battalion built from fired brick — the first such structure in San Diego — stood on the plaza that is now the center of Old Town San Diego State Historic Park. The building is gone now, as most early California construction is gone, but its location is documented and commemorated as part of the historic district.

Old Town preserves the period from 1820 to 1870, which means the battalion's arrival and construction projects fall within its interpretive scope. The story of those months — the exhausted soldiers who had just completed an impossible march, building a courthouse in a Mexican town that had just become an American one — is embedded in the layered history of a place that has always been more complicated than its postcard image suggests.