Isaac Green Messec, sometimes Messic or Messick (1823–1901) was a Texas Ranger, 49er, miner, businessman, California Milita Captain, County Sheriff, Sergeant-at-Arms of the California State Senate and rancher, a well-known figure in political and mining circles early in the history of the State of California.
Isaac Green Messec, was born in Macon, Bibb County, Georgia. in 1823. Before 1843, his family migrated to Shelby County in East Texas. Raised in Texas, he became a Texas Ranger. In the Mexican war, he fought in one of the units of Texas Rangers under General Zachary Taylor.
In 1849, Messec joined in the California Gold Rush, leaving East Texas for California with a party of fifty men, he crossed the entire state of Texas, turned south at El Paso into Chihuahua, Mexico to avoid the Apache, crossed into Sonora by way of the Guadalupe Pass, followed the trail through the future Gadsden Purchase territory to the Gila River, and rode down the Gila to the Colorado River. Fording the Colorado at the future site of Fort Yuma, they crossed the desert to Warner's Ranch and traveled onward to Los Angeles and thence to San Francisco.