The
Transcontinental Railroad wasn't completed until four years after the
Civil War ended. It wouldn't have made much of a difference if it was
completed before the war as it only ran east to west, not north to
south.
The first battle between iron-clad ships took place during the Civil War (1862). It made wooden naval ships obsolete.
The Gatling gun was invented during the Civil War. It was the forerunner of modern machine guns.
The Civil War saw the first use of repeating rifles in war.
