1840:
General Canales rejects terms of peace offer and continues to fight for independence for Republic of the Rio Grande.
1848:
United States demands Baja California at Treaty of Guadalupe-Hidalgo as well as an independent Republic of the Rio Grande.
Yucatan independence recognized by United States.
1853:
Much larger Gadsen Purchase. US buys all of Sonora State.
1928: After 18-years of war, Mexican Revolution ends in stalemate. Nation is split in two, southern half ruled by Zapata.
1933: Chiapas declares independence from Republic of Southern Mexico after death of Zapata.
1941: Chiapas independence established after 8-year war. Loss of Chiapas allows North Mexico to reabsorb South Mexico. However, several cities (Oaxca and Acapulco) refuse and become San Marino like city states.
End result is a Mexico that looks like this: