Short answers, pulled from the story.
The Battle of Fort Henry was fought on the 6th of February, 1862, in Stewart County, Tennessee. The bombardment lasted 75 minutes, and Brig. Gen. Lloyd Tilghman surrendered to Union Flag Officer Andrew Hull Foote before Grant's army even arrived at the fort.
The Union won the Battle of Fort Henry. It was the first important Union victory in the Western Theater, and the first significant success for Brig. Gen. Ulysses S. Grant. The victory opened the Tennessee River to Union military traffic as far south as the Alabama border.
Fort Henry fell quickly because of a combination of factors: the fort was built on low, swampy ground prone to flooding, heavy February rains submerged most of the fort including the powder magazine, only nine guns remained above water to mount a defense, and Union naval gunfire from ironclad gunboats was both accurate and effective. Brig. Gen. Tilghman had already evacuated the bulk of his garrison before the battle began.
Union land forces were commanded by Brig. Gen. Ulysses S. Grant, with two divisions under Brig. Gens. John A. McClernand and Charles F. Smith. The naval flotilla was commanded by Flag Officer Andrew Hull Foote, with the timberclad gunboats under Lt. Seth Ledyard Phelps. The naval forces accepted the fort's surrender before Grant's troops arrived.
Fort Henry was completely underwater by the 8th of February 1862, just two days after the battle. When the Tennessee River was dammed in the 1930s, creating Kentucky Lake, the remains of Fort Henry were permanently submerged. A small navigation beacon far from the Kentucky shoreline now marks the location of the fort's northwest corner.
After the fort surrendered, Flag Officer Foote sent Phelps with the three timberclad gunboats, Tyler, Conestoga, and Lexington, on a raid upriver. Phelps reached Muscle Shoals near Florence, Alabama, destroyed supplies and a Memphis and Ohio Railroad bridge 25 miles upriver, and captured Confederate vessels including the ironclad Eastport, which was still under construction. His raiders returned to Fort Henry on February 12.