 Complete the following phrase:  Buenos Aires also attracted migrants from Argentinas provinces and neighboring countries. Shanty towns villas miseria started growing around the citys industrial areas during the 1930s, leading to pervasive social problems and social contrasts with the largely upwardly-mobile Buenos Aires population. These laborers became the political base of Peronism, which emerged in Buenos Aires during the pivotal demonstration of 17 October 1945, at the Plaza de Mayo. Industrial workers of the Greater Buenos Aires industrial belt have been Peronisms main support base ever since, and Plaza de Mayo became the site for demonstrations and many of the countrys political events; on 16 June 1955, however, a splinter faction of the Navy bombed the Plaza de Mayo area, killing 364 civilians see 