Modernismo began in Latin America in the late 1800s and spread to Spain in the first decades of the twentieth century. While its greatest influences were French symbolism and the Parnassian school of poets, elements of classical Spanish poetry and the influence of American poets like Edgar Allan Poe and Walt Whitman could also be detected in the work of the movement.
Practicioners of modernismo often set their poems in exotic landscapes dotted with swans, peacocks, lilies, princesses, and other symbols of nobility and aristocracy. Although these beautiful symbols may have seemed purely escapist, they were meant to emphasize the materialism and vulgarity of everyday life by creating a world of unadulterated beauty.
The Cuban poet and revolutationary José Martí was a forerunner to the movement, which can trace its birth to the publication of Nicaraguan poet Rubén Darío's book Azul (Blue) in 1888, regarded as an international sensation. Modernismo became one of the first Latin American artistic movements to influence the Spanish peninsula, notably influencing such writers as Antonio Machado, Juan Ramón Jiménez, and other members of the Generation of '98.
Although the movement itself was largely over by 1920, it continued to influence Spanish and Latin American poets throughout the rest of the twentieth century, including a Brazilian renaissance in 1922 also named "modernismo" largely enacted by Mário and Oswald de Andrade.
Spanish speakers can find more information online at Modernismo en Espana e Hispanoamerica.