Pará participated in the Passagem de Humaitá in February 1868 and provided fire support for the army for the rest of the war.

The Pará-class monitors were designed to meet the need of the Brazilian Navy for small, shallow-draft armored ships capable of withstanding heavy fire.

The monitor configuration was chosen as a turreted design did not have the same problems engaging enemy ships and fortifications as did the casemate ironclads already in Brazilian service.

The engines produced a total of 180 indicated horsepower (130 kW) which gave the monitors a maximum speed of 8 knots (15 km/h; 9.2 mph) in calm waters.

[3] Pará carried a single 70-pounder Whitworth rifled muzzle loader (RML) in her gun turret.

[5] Most unusually the gun's Brazilian-designed iron carriage was designed to pivot vertically at the muzzle; this was done to minimize the size of the gunport through which splinters and shells could enter.

She was towed to the Río de la Plata on 20 June 1867 and steamed up the Paraná River, although her passage further north was barred by the Paraguayan fortifications at Humaitá.

Pará and her two sister ships, Alagoas and Rio Grande, were lashed to the larger ironclads in case any engines were disabled by the Paraguayan guns.

On 15 October she bombarded Angostura Fort in company with Brasil, Silvado, Rio Grande and her sister Ceará.