Prior to the Chinese conquest of the Red River delta region, the Vietnamese and the Muong formed a fairly unified group. The forefathers of the Viet peoples migrated down the plains and became influenced by the Han Chinese. However, the Muong's ancestors stayed in the mountains, preserving their culture, rejecting the influence of the Chinese. Thus, the two groups developed independently. Since 1954, the Socialist Republic of Vietnam has made efforts to conform the Muong into the mainstream structure of the nation.

      It is thought that this split began about two-three centuries after the birth of Christ.  But the Viet and the Muong had lived in the northern area of Vietnam for many centuries before then.  The Muong certainly have not been noted for migrations.  They have continued to reside in the land of their ancestors for thousands of years.