United Mexican States (modern)
Who & why: the Mexican Revolution (1910–1920), a sweeping and costly conflict against Porfirio Díaz's long dictatorship and its successors, produces the progressive 1917 Constitution that still governs Mexico today. The eagle emblem is refined again in 1968, ahead of the Mexico City Olympics, into its current, more naturalistic form.
What it represents: green, white and red frame the eagle-and-cactus-and-serpent emblem from the Mexica legend. Wikipedia says the colours' meanings have changed over time and that the law gives no official symbolism; Flags of the World records green as hope or the territory, white as unity or the people, and red as the blood of the national heroes or the struggle for independence.
Wikipedia says the current flag was adopted on 16 September 1968 and confirmed by law on 24 February 1984, that a presidential decree of 1916 changed the eagle from front-facing to side-facing, and that a rule on the reverse side's eagle was published on 9 May 1995. FOTW says a decree of 17 August 1968 in the Diario Oficial adopted the flag and arms, that a decree of 8 February 1984 confirmed them, and that the law of 24 February 1984 did not change the design.
- Flag of Mexico — Wikipedia compiled
- Mexico — Flags of the World (CRW Flags) compiled
Not established: The 1968 dates differ between the sources (16 September, 17 August, and this page's earlier 24 September). The era starts in 1917 and the sources date the current design to 1968. The colours' meanings are disputed and the law gives none.