The monument was unveiled on 15.07.1945 on the anniversary of the Battle of Grunwald. However, it found its way to America much earlier, in May 1939 it was placed in front of the entrance to the Polish Pavilion at the World Exhibition in New York. After its completion, it was to be unveiled in one of the major Polish cities, but these plans were thwarted by the Second World War. Appreciating the high class of the sculpture, but also taking into account the political situation and the meaning of the sculpture, the city authorities decided to keep it for New York. Upon arriving there in 1941, Ostrowski gained the support of the city mayor for the idea and organised a social committee for the public display of the monument. Here, the artist used the traditional formula of the equestrian monument: on a stone pedestal, a rider in knightly attire, wearing a crown on his head, sitting on a horse, holding two crossed swords.

It fitted in with the historicist design of the entire Polish presentation at the New York exhibition, in which only the ultra-modern tower in front of the pavilion stood out. However, it too was given a traditionalist interpretation: "The tower is square, openwork, built of iron covered with gold paint; it was modelled on Polish medieval towers. In fact, the whole design of the pavilion (...) is a combination of modernity of drawing with the tradition of the Polish Middle Ages" (J. Prądzyński, 1939). Ostrowski's 'knight' was, of course, the strongest accent of this tradition - up to the very last moment there was pressure on the artist (politically motivated, due to Polish-German tensions) to make his Jagiełło become Bolesław Chrobry.

Ostrowski designed the Grunwald monument as early as 1909. The 1939 Pavilion exhibition also featured his statue of Józef Piłsudski inside. The monument gained great popularity, it was even considered the most popular monument in New York in the USA.