I am looking for information on my Great Grandfather Ferdinand Brandl/Brandel who immigrated to the US in 1888. He was married to Anna Moser/Mose. He had a son George

In the book "Declaration of Intent to Become a Citizen, Dubuque County, Iowa". Ferdinand Brandl signed a declaration of intent to become a citizen on Oct 20, 1891. Further, he was 27 years old at the time he signed, he was "Bavarian" and landed in this country 03 Oct 1888.