Indiana was the 19th state to join the Union.
Indiana was admitted into the Union on December 11, 1816 becoming the 19th state to join the union.
Indiana was admitted to the Union on December 11, 1816 becoming the 19th state admitted to the Union.
Indiana
Indiana was admitted into the Union on December 11, 1816 becoming the 19th state to join the union.
Mississippi was admitted into the Union on December 10, 1817 becoming the 20th state to join the Union.
Indiana was admitted to the Union on December 11, 1816 becoming the 19th state to join the union.
Indiana was admitted into the Union on December 11, 1816 becoming the 19th state to join the union.
Indiana was admitted into the Union on December 11, 1816 becoming the 19th state to join the union.
Indiana was admitted into the Union on December 11, 1816 becoming the 19th state to join the union.
Illinois was admitted to the Union on December 3, 1818 becoming the 21st state to join the union.
If you are a US citizen you are the Union. Any state that may, in the future, join the Union would become US citizens. If you are referring to a workers union then it depends on the constitution of that union. There are several international ones.