Argentina , officially the Argentine Republic, is a federal republic
What do you mean by federal republic?
The Basic Law for the Federal Republic is the constitution 
What is Argentian's constitution called?
Not sure, but The adoption of the Constitution was preceded by a period of agitation
How long did the agitation last?
Argentina rose as the successor state of the Viceroyalty of the Río de la Plata, founded in 1776.
Really? It declared its independence the same time the US did?