The Union flag, is called the Stars and Stripes, symbolized solidarity and patriotism

https://troynfmn638.huicopper.com/a-closer-look-at-historic-civil-war-flags-what-they-represent

The Union flag, known as the Stars and Stripes, symbolized harmony and patriotism, featuring 13 stripes and a container of blue with stars that represented each country inside the union.