investment. The main port was also built and inaugurated in 1916.
1930–1946: A military coup reinstated the Conservative hegemony in politics through electoral fraud and corruption, but in the local level they were quite progressive, their policies viewed in some way as a continuity of the socialist trend. The seaside Casino complex opened in 1939, was designed by architect Alejandro Bustillo, and Highway 2, the main road to Buenos Aires, also dates from this period.
1946–1955: Birth of the Peronist movement. A coalition between socialists and radicals defeated this new party by a narrow margin in Mar del Plata, but by 1948 the Peronism will dominate the local administration. The massive tourism, triggered by the welfare politics of Perón and the surge of the middle class marked a huge growth in the city's economy.
1955–1970: After the fall of Perón, the socialists regained the upper hand in local politics; the city reached the peak in activities like construction business and building industry. Massive immigration from other regions of Argentina.
1970–1989: Slight decline of tourism demand, counterbalanced by the increasing of other industries such as fishing and machinery. General infrastructure renewal under the military rule. The centrist Radical Civic Union becomes the main political force after the return of Democracy in 1983.
1989–present: Though the Peronism replaced the radicals in central government amid a national financial crisis, the latter party continued to rule in Mar del Plata. Some resurge of mass tourism in the early '90s was followed by a deep social crisis in town, with an increase of poverty, jobless rate and emigration. By contrast, the first decade of the 21st century shows an amazingly quick recovery in all sectors of the ailing economy.
In November 2005 the city hosted the 4th Summit of the Americas
