Guns of Bull Run by Joseph Alexander Altsheler

The first volume in the Civil War series, following the adventures of Harry Kenton, who leaves his home in Kentucky. He travels through dangerous territory to South Carolina on a secret mission on the eve of the Civil War. (From Chapter 4) "They will not fire! They dare not!" cried Shepard in a tense, strained whisper. As the last word left his lips there was a heavy crash. A tongue of fire leaped from one of the batteries, followed by a gush of smoke, and a round shot whistled over the Star of the West. A tremendous shout came from the crowd, then it was silent, while that tongue of flame leaped a second time from the mouth of a cannon. Harry saw the water spring up, a spire of white foam, near the steamer, and a moment later a third shot clipped the water close by. He did not know whether the gunners were firing directly at the vessel or merely meant to warn her that she came nearer at her peril, but in any event, the effect was the same. South Carolina with her cannon was warning a foreign ship, the ship of an enemy, to keep away. The Star of the West slowed down and stopped. Then another shout, more tremendous than ever, a shout of triumph, came from the crowd, but Harry felt a chill strike to his heart. Young St. Clair, too, was silent and Harry saw a shadow on his face. He looked for Shepard, but he was gone and the boy had not heard him go. "It is all over," said St. Clair, with the certainty of prophecy. "The cannon have spoken and it is war.