Gulnac and Weber dissolved their partnership in 1843. Gulnac's attempts to settle the Rancho Campo de los Franceses failed, and Weber acquired it in 1845. In 1846 Weber had induced a number of settlers to locate on the rancho, when the Mexican–American War broke out. Considered a Californio, Weber was offered the position of captain by Mexican Gen. José Castro, which he declined; he later, however, accepted the position of captain in the Cavalry of the United States. Capt. Weber's decision to change sides lost him a great deal of the trust he had built up among his Mexican business partners. As a result, he moved to the grant in 1847 and sold his business in San Jose in 1849.