This substantial piece from the newsletter of the Mickiewicz Institute nicely delineates the high points and significance of his career: he arrived in the new United States in 1776, and during the war, he designed the fortifications at West Point and was responsible for the American campaign at Saratoga, which was decisive for the success of the Revolution, not least because it moved the French to lend their full backing to the new nation's struggle. In Poland, he famously led his nation's forces in the revolutionary struggles of 1791 and 1794. Although Kościuszko is celebrated for his dedication to the rights of peasants and Jews, his equally passionate commitment to the rights of enslaved Africans and Native Americans in the new United States is less well known. (more on the latter topic here)
In Philadephia, the house where he resided has been preserved and turned into the Thaddeus Kosciuszko National Memorial, operated by the National Park Service.
He is commemorated at West Point with a monument by John Latrobe (1828; incorrectly labeled a tomb in the engraving below), to which a statue was added in 1913.
Marker in the main square in Kraków, at the spot from which Kościuszko announced the revolution in 1794.
Kościuszko monument by Leonard Marconi and Antoni Popiel (1900) outside the Wawel royal castle, Kraków. The Austro-Hungarian monarchy forbade such commemorations, so it was erected only during the interwar years. The Nazi occupiers, who located their headquarters in the castle, destroyed the statue. The 1960 reproduction now on the site was a gift of reconciliation from Dresden, East Germany.