 In 1835 he was elected Brazoria "alcalde" and was one of the four representatives of Brazoria who attended the convention at Washington-on-the-Brazos in 1836, where he signed the Texas Declaration of Independence.Since Brigham had been influential in the founding of a Masonic Lodge in Brazoria, he served as a charter member of the Masonic Grand Lodge of Texas in Houston on December 20, 1837.He was appointed auditor of the Republic of Texas by David G. Burnet and named Texas's first treasurer by President Sam Houston in December 1836.