In addition to being Constitution Day, September 17th is also Citizenship Day. Both days were designated by 36 U.S.C. §106.
Constitution Day and Citizenship Day first began in 1940 (54 Stat. 178). Called I am an American Day, the holiday was set on the third Sunday of each May as a "recognition of all who, by coming of age or naturalization, have attained the status of citizenship." In 1952, Public Law 261 (66 Stat. 9) repealed the 1940 resolution, renamed the commemoration Citizenship Day, and added the statement that the holiday also celebrates "the formation and signing, on September 17, 1787, of the Constitution of the United States." Constitution Day was added to the holiday's title with the passage of Public Law 108-447, the Consolidated Appropriations Act of 2005. See pages 536-537 of the nearly 700 page law.
The U.S. Citizenship and Immigration Services website has many resources for those interested in becoming a U.S. citizen, including forms that can be submitted by mail and forms that can be filed electronically. There are also guides to and study materials for the Naturalization Test.
In Utah, citizenship education classes are often provided by cultural associations or school districts. The Asian Association of Utah, for instance, offers citizenship test preparation classes. United Way of Utah County offers citizenship test preparation in Provo. The Granite School District offers a citizenship class as part of its lifelong learning department.