In the Fall of 1812, Johnson made a contract with the County Commissioners, Messrs. Wright, Ruggles and Miles, to build a Court House and Jail on the Public Square, opposite where the First Presbyterian Church now stands. The material was to be logs, laid end-wise for greater security. The work was pushed forward rapidly the next Summer, and towards noon of September 12th, Johnson and his men were just putting the finishing touches to the building, when they were startled by what seemed the roar of distant thunder. On looking out of the windows not a cloud could be seen in the sky, but the reverberations continued, and at once the conviction that the noise was of cannons seized them. Throwing down their tools they ran to the bank of the lake, where nearly all the villagers at home to the number of about thirty, were already gathered, stretching their eyes to the westward, whence the sounds came. Now the reports of the cannon could be plainly distinguished. They knew that Perry's fleet had passed up the lake, and that, consequently, a battle could be at any moment expected. The louder reports told when the Americans fired, for their guns were of heavier caliber than the English. At last the firing ceased for a while. Then three loud reports, evidently American, were heard, and the little crowd, convinced that their side had won, gave three hearty cheers for Perry. About two days afterwards, Johnson and a man named Rumidge picked up a large flat-boat that had been built by General Jessup for the conveyance of troops, and then abandoned. Each of the finders purchased a hundred bushels of potatoes, took them to the army at Put-in-Bay, quadrupling the money invested, and giving Johnson his first financial start in life. As General Jessup needed the boat to transfer his troops to Malden, he retained it, taking Rumidge also into service, and leaving Johnson to return to Cleveland on the gunboat Somers, of which he was made pilot for the voyage. Shortly afterwards Rumidge returned with the boat and brought news that the American forces had fought a battle with the British at Moravian Town. Johnson resumed command of the flat-boat, and with his associate freighted it with supplies for the army at Detroit. The speculation was successful, and Johnson engaged with the quartermaster of the post to bring a cargo of clothing from Cleveland to Detroit. The season was far advanced, and the voyage was cut short by the ice in the upper part of the lake, so that the boat was headed for Huron, where the cargo was landed and the freight for that distance paid.