An adventuresome Tennessee lawyer, John Neely Bryan (1810-1877), arrived in the area in 1841. His first encampment was on a high bluff overlooking where the Trinity River then flowed (near today's Dealey Plaza). While acknowledged as an industrious fellow, Bryan met with only marginal success in persuading others to help settle the area.
After a bitter winter when supplies ran low and Indian attacks persisted, Bryan did, however, succeed in staking claim to the land and giving its name. While historians disagree, one official historical marker, proclaims that, indeed, the city was named in honor of George Mifflin Dallas (1792-1864).
Dallas was a Pennsylvania lawyer who also served in various diplomatic capacities. His most notable claim to fame was election as Vice President of the United States in 1844 under President James K. Polk. Polk and Dallas ran on a pro-Texas annexation platform, so that may account for Bryan's city name choice.
Bryan himself led an undistinguished life thereafter, being committed by his family to the state mental hospital. His death and burial in the hospital's cemetery went unnoticed by the newspapers of the day.