President Barack Obama spoke for the first time as president at a U.S. mosque on February 3, 2016. His choice was the Muslim Brotherhood-linked Islamic Society of Baltimore mosque, where he portrayed Islam as having "always been part of America."
The Islamic Society of Baltimore was established in 1969. If Obama had wanted to speak at "the oldest purpose-built mosque that is still in use today" in the United States, in order to try to demonstrate that Islam has "always been part of America," he would have found it in Cedar Rapids, Iowa. It would not have helped his cause, however. This mosque, known as "the Mother Mosque of America," dates way back – drum roll, please – to 1934. The oldest mosque in the U.S. was built in North Dakota in 1929.
To provide some perspective on how short a time it has been since the first mosques in the United States were built, the Touro Synagogue in Newport, Rhode Island, the oldest surviving Jewish synagogue building in North America, was completed in 1763.