Pentagon officials traveled last week to Fort Leavenworth in Kansas, home to the military’s only domestic maximum-security prison, to evaluate it as a potential alternative to the detention facility at Guantánamo Bay, a Defense Department spokesman said Monday.

The Naval Consolidated Brig in Charleston, S.C., is the only other military base department officials are considering as they prepare to send Congress a detailed proposal to shutter Guantánamo, which the Obama administration has tried and failed to close since 2009. Non-military sites are also in play, but spokesman Navy Capt. Jeff Davis declined to provide specific locations.