Greetings Cosmic Americans!
During the war, Washington City was the most heavily fortified city in the United States or the Confederacy. Indeed it was. What's more, according to the Civil War Trust website, the city was more than likely the most fortified in the world.
Surrounding the capital, there were 68 enclosed forts with 807 mounted cannon, 93 mortars and over 20 miles of rifle trenches. There were military roads, telegraph lines, storehouses, and all kinds of camps - all of which ringed the city.
But did the Rebs ever really consider taking Washington? Not likely. Sure there were a few shot at the city - such as Jubal Early's famous raid in July 1864 - but that was merely a threat, meant to relieve the pressure on Lee's army in Virginia. Other Confederates considered trying to get between Washington and the Army of the Potomac - Longstreet's famous plea to Lee during the Gettysburg campaign was exactly that sort of plan. But nothing came of it.
Any threats on Washington were really only that - threats. Meant more to make the people of the North nervous or to draw Union troops away from the principal Rebel Army operating in the East.
In wartime, taking your opponent's capital seems like a good idea. Remember the Union's early war cry...On to Richmond!!!! But there was no equivalent - On to Washington! resonating in the South. They didn't need to capture the United States capital - the Rebs only needed to wear the northern fighting spirit down to a nub - which they almost did....almost.
The truth is, the Union army didn't really need to go after Richmond, either. U.S. Grant surely knew this. He saw the Army of Northern Virginia as the life blood of the Confederacy. Destroy the army, he thought, the rest will fall in to place. Richmond was evacuated in the last days of the war when Grant began the final chase to Appomattox - it was not taken by force. What do you know...he was right.