Captain José Montanha drew the plans in 1790, working under the colonial administrator José Marcelino de Figueiredo. The building was conceived as half of a pair, joined to the old government palace next door, a tidy emblem of imperial order on the southern frontier. The order did not hold. In that very same year the legislative chamber went into recess, and soon the region was convulsed by the Ragamuffin War, the long separatist rebellion that gives the modern state assembly its name. The palace beside it would eventually be demolished to make room for the Piratini Palace. Its smaller companion endured, and the decades of silence had only just begun.

Few legislatures have been interrupted as often as the one that met here. The chamber reopened in 1845, only to fall dark again between 1865 and 1870 during the Paraguayan War. It shut once more from 1937 to 1947, when Getúlio Vargas dissolved the legislatures of his Estado Novo. Each silence ended in renewal. The deputies returned in 1947 for a new constituent assembly, and the building served until 1967, when lawmakers moved to the modern Farroupilha Palace. To stand inside the Casa da Junta is to occupy a room that has been emptied by war, by dictatorship, by the ordinary churn of politics, and filled again every single time.

The architecture rewards a slow look. When it was first built the Casa da Junta rose only a single floor, a plain colonial box. The remodel of 1860 added a story and recast the whole in a more fashionable dress. A round-arched doorway sits at the center, flanked by two groups of three arched windows in careful symmetry. On the upper floor the openings become doors, fronted by parapets of worked metal and separated by slender Ionic pilasters. Above the lower and upper windows, blind tympanums hold panes of clear stained glass without images. On the gabled flanks, a triangular pediment is pierced by four small oculi, and beneath them a pair of round-arched windows survive from the original colonial design, the last visible traces of the building's first, humbler self.

Recognition came in 1981, when the state listed the building as protected heritage. A restoration the following year turned it over to the Civil House of the state government, and in 2004 ownership returned to the Legislative Assembly, where it began a new life as the seat of the Legislative Memorial. The story carried a fitting coda in 2023, when the gaúcho legislature convened a session inside its oldest home for the first time since 1967. After more than half a century, lawmakers once again filled the room where their predecessors had argued the fate of a frontier province, completing a circle that had taken 233 years to close.

What makes the Casa da Junta worth seeking out is precisely how alone it stands in time. Porto Alegre grew up around the cattle trade and the river port, a young city by the standards of colonial Brazil, and it has never been sentimental about its old buildings; the viaduct-building decades of the twentieth century erased many that deserved better. Out of all of it, this one modest structure is the sole survivor from the 1700s, the only door in the entire city you can walk through and know that Azorean colonists and frontier governors walked through it too. Everything else from that founding generation is gone. The Casa da Junta remembers for the rest.