Definition: Rewrite each original sentence in order to make it easier to understand by non-native speakers of English. You can do so by replacing complex words with simpler synonyms (i.e. paraphrasing), deleting unimportant information (i.e. compression), and/or splitting a long complex sentence into several simpler ones. The final simplified sentences need to be grammatical, fluent, and retain the main ideas of their original counterparts without altering their meanings.
Input: United States admission day (1889) of North Dakota and South Dakota as 39th and 40th states.

United States added North Dakota and South Dakota as 39th and 40th states in 1889.