On December 11, 1862, the Union Army of the Potomac crosses the Rappahannock River at Fredericksburg, Virginia. Here's how Confederate Lieutenant General James Longstreet remembered the event:
On the morning of the 11th of December, 1862, an hour or so before daylight, the slumbering Confederates were awakened by a solitary cannon thundering on the heights of Marye's Hill. Again it boomed, and instantly the aroused Confederates recognized the signal of the Washington Artillery and knew that the Federal troops were preparing to cross the Rappahannock to give us the expected battle. The Federals came down to the river's edge and began the construction of their bridges, when Barksdale opened fire with such effect that they were forced to retire. Again and again they made an effort to cross, but each time they were met and repulsed by the well-directed bullets of the Mississippians. This contest lasted until 1 o'clock, when the Federals, with angry desperation, turned their whole available force of artillery on the little city, and sent down from the heights a perfect storm of shot and shell, crushing the houses with a cyclone of fiery metal. From our position on the heights we saw the batteries hurling an avalanche upon the town whose only offense was that near its edge in a snug retreat nestled three thousand Confederate hornets that were stinging the Army of the Potomac into a frenzy. It was terrific, the pandemonium which that little squad of Confederates had provoked. The town caught fire in several places, shells crashed and burst, and solid shot rained like hail. In the midst of the successive crashes could be heard the shouts and yells of those engaged in the struggle, while the smoke rose from the burning city and the flames, leaped about, making a scene which can never be effaced from the memory of those who saw it. But, in the midst of all this fury, the little brigade of Mississippians clung to their work. At last, when I had everything in readiness, I sent a peremptory order to Barksdale to withdraw, which he did, fighting as he retired before the Federals, who had by that time succeeded in landing a number of their troops. The Federals then constructed their pontoons without molestation, and during the night and the following day the grand division of Sumner passed over into Fredericksburg.
About a mile and a half below the town, where the Deep Run empties into the Rappahannock, General Franklin had been allowed without serious opposition to throw two pontoon-bridges on the 11th, and his grand division passed over and massed on the level bottoms opposite Hamilton's Crossing, thus placing himself in front of Stonewall Jackson's corps. The 11th and 12th were thus spent by the Federals in crossing the river and preparing for battle.
Opposite Fredericksburg, the formation along the river-bank was such that the Federals were concealed in their approaches, and, availing themselves of this advantage, they succeeded in crossing and concealing the grand division of Sumner and, later, a part of Hooker's grand division in the city of Fredericksburg, and so disposing of Franklin in the open plain below as to give out the impression that the great force was with the latter and about to oppose Jackson.