The Americans eventually constructed such obstacles across the river at northern Manhattan, between forts Washington and Lee in 1776; at the newly constructed Fort Montgomery on the West Bank on Popolopen Creek in 1776–1777 south of West Point; a partially completed one at Pollepel Island in 1776–1777 north of West Point; and the Great Chain (1778–1782) between West Point and Constitution Island. The largest and most important project was the last-mentioned chain, at West Point, which was reset each spring until the end of the war. Attention was concentrated on the West Point area because the river narrowed there, and curved so sharply that, together with winds, tides and current, ships already had to slow to navigate the passage. Creating more obstructions on the river enabled the shore batteries to work their cannons against the enemy.