The whole island serves as a memorial to the 26th President of the US, Theodore "Teddy" Roosevelt. Apart from seeing the statue of the president and the adjoining fountain, there's a lot to do on the island - join a ranger-led tour, explore a variety of walking trails, or enjoy some birdwatching.
Daily: 6 am - 10 pm
Free admission.
Wikipedia https://en.wikipedia.org/wiki/Theodore_Roosevelt_Island
Official Website https://www.nps.gov/this/index.htm
Coordinates 38°53'46.292" N -77°3'45.454" E