Portal codes 1911

My Grandmother, Karen Arnesen, departed Liverpool England on 3-11-1911 on the Virginian. Last residence Norway.. The inspection card I have states "passed Quarnteen..Port of U.S. and then the letter E.. and a stamp. Is the letter E the port she came through?? The Virginian was an Allan Line ship and made sereral stops with most being Canada. Her obit. says she landed in Bottineau, North Dakota, so I think she could have taken the train from Canada to N.D... Any input would be appreciated. Elouise