The National Archives and Records Administration is the National Archive of the United States. Their website is archive.gov. They are tasked with the preservation of important documents of the United States. Their collection includes the Declaration of Independence, the Constitution, the Bill of Rights, Immigration Records, Military Records, Records of Act of Congress, Court Records, Presidential Records, and many others.
NARA has a treasure trove of records for the genealogist, much of which has not yet been digitized or placed online, and nearly all of which is available for use. Some of the most useful records in the collection, for genealogists, are the Census of the United States, records of military service, immigration and naturalization records, and land records.
The nearest location to Morgan is in Denver, but records can be ordered online or via mail. If you decide to visit in the office in person it is important to prepare. The NARA website provides good advice on preparing for a visit to get the most out of it.
NARA has been working with several organizations to make records available online. FamilySearch has extensive records from the Revolutionary War, the Civil War, the war of 1812, and World War II. Fold3.com has records of the Mexican and Indian War, the Revolutionary War, and the Vietnam War. The Ellis Island immigration records can be found at ellisisland.org and on FamilySearch.org.
Many of the land records and military service records cannot yet be found online, however, and these records often contain substantial historical and genealogical data. These records can be ordered online or viewed at a NARA location.
The NARA website also has extensive online help materials to assist in understanding their records and how to use them. They have finding aids, training, and links to video courses to help with using and understanding their collection. They will also provide limited help on locating and using their records from a distance.
If you have never been to the NARA website, go and have a look. There are very few better sources for United States records than those held by NARA. It takes some time and patience to learn how to access and use the records, but the wealth of information found will be well worth the investment.