The first mention of Carlsbad in the annals of history was hardly flattering. In 1769, a contingent of Spanish explorers, led by Don Gaspar de Portola, was plodding its way into Alta California to claim the territory for the King of Spain.  Included in the expedition was missionary Fray Juan Crespi, who recorded a brief stop at a lagoon. Resting downwind from a garbage pile of an Indian Village, the troops christened the lagoon for posterity: Agua Hedionda (Stinking Water). Following in their footsteps were more soldiers and priests, to establish pueblos and missions to ensure Spain's hold on its remote territory. To convert the friendly local Indians to Christianity, the Franciscan missionaries, in 1798, established Mission San Luis Rey several miles north of the lagoon. The mission known as The King of Missions  became the largest of 21 missions in California extending over 20 square miles with herds of cattle, extensive crops and administering the lives of 2,000 Indian residents.

 In 1833 the rich mission holdings were secularized and divided into large land grants of several thousand acres each. Initially claimed by influential Californios, the large ranches, over the next half century were sub-divided and sold off. With the coming of the railroad in 1883, the land between Los Angeles and San Diego was opened up to homesteaders.

The Carlsbad depot was built in 1887 by the Arizona Eastern Railway. The Depot also served as a telegraph office, Post Office, Wells Fargo Express Office and general store. Purchased by the Atchison, Topeka and Santa Fe Railroad in 1905, the depot was shipping point for locally grown fruit, vegetables and flowers.  Closed in 1960, the building was deeded to the city. It now serves as the Tourist Information Center to provide information and assistance to the many tourists who visit Carlsbad.