"With the outbreak of hostilities in April 1861, it became necessary to begin preparing the defenses of Washington, DC. In 1857, Albert Boschke, a German born civil engineer, published his Map of Washington City, District of Columbia, seat of the federal government: respectfully dedicated to the Senate and the House of Representatives of the United States of North America which showed, for the first time, the location of every structure in the city as of the publication date."
Checkout Boschke's 1857 and 1861 map of the 'ten mile square' here.
1861 is also a date of great import as it was the first year Robert Portner began operating in Alexandria. He and his business partner Frederick Recker, had ventured down from New York while Portner visited a cousin of his stationed, as so many Union soldiers were, in Alexandria. As Garrett Peck writes in his book Capital Beer: "The two friends decided to buy a grocery store at King and St. Asaph streets, a store they named Portner and Recker. It opened on September 2, 1861. (The store is now the site of Columbia Firehouse, 109 S. St. Asaph Street.)" The grocers sold beer from New York and by 1862 a brewery was born. "The Portner and Company brewery opened on the northeast corner of King and Fayette streets and brewed almost 2,000 barrels of beer during the war." Peck goes on to write, "In the decades after the war, Portner would become the largest brewer in the South."
Inside the contemporary boundary of the District, John Kozel, a German immigrant from Wurttemberg, operated a small brewery at Ninth and M Streets, NW. In 1861, he moved to a larger facility at 43 N Street, NW. Kozel's advertisements list his as a lager and weiss beer brewery. Ernst Loeffler (ad below) also ran a brewery and "pleasure garden" nearby on the corner of New York Avenue and First street. On the same page as Barclay & Perkins mild ale and mild porter is "Cream Ale" from Philadelphia, and Loeffler's "lager beer."
In the 1860 Census, Loeffler was listed as a "lager beer brewer" so not much for Washington mild ale! It is of interest to beer historians that both English mild and Washington-brewed lager shared the same copy space. The following text is taken from Loeffler's ad in the Republican:
"Ernest Loeffler takes this method to announce to his friends and the public generally that he has opened his garden, on the corner of N.Y. avenue, and First street, for the reception of visiters for the season. Music on Mondayand Thursday evenings, and sacred concerts on Sunday evenings. He has always a large supply of refreshments, wines, liquors, &c. Also, the very best lager beer from his own brewery. He also furnishes lager beer to persons throughout the city. A bowling alley and gymnasium have been fitted up for the accommodation of visiters. May 24."

"He was so delighted that he could not refuse the hospitality of the sturdy brewers, who pressed upon him the various kinds of malt liquor. He began with mild porter, and went up to the strongest stout; then renewed the attack on mild ale, and finished with XXXX. All went well enough while he was in the cool vaults, but, like many other people who have gone over this remarkable brewery, when he came into the open air he saw three or four broughams (carriages) instead of one."

Cream Ale! Cream Ale! The subscriber has the pleasure of informing the public that he has become sole agent for the sale of Martin's Justly Celebrated Cream Ale, appreciated by all who have tried it as a nutritive, delicious, wholesome beverage. He has also been appointed sole agent for the sale of Bergler's Philadelphia Sparkling Stock Ale.