The first flag of the Republic of Peru was created by General José de San Martín, and officially decreed on 21 October 1820. It is diagonally quartered, with white upper and lower fields, and the others red.

The flag was defaced with an oval-shaped laurel crown in the center, surrounding a sun rising behind mountains by the sea. The symbolism of the flag's colors is uncertain, but according to Peruvian author Abraham Valdelomar, San Martín, having arrived on the coast of southern Pisco, was inspired by the colors of parihuanas, red-and-white flamingos.

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