Most graduate programs are accredited by the accrediting body/organization of that field or discipline. For example, the American Library Association accredits master of library science programs. For students interested in this field, it is important to find a program that has been recently accredited, or finding a job after graduation may be difficult. Finding out which organization accredits the type of program you're interested in is key to determining your potential school's accreditation status. Checking with a professor in that field, talking to a librarian, or contacting the school itself are some of the ways to gather this information.
Tip: To find out which organization, accredits the program(s) you're interested in, you can Google the national association of the field and check that association’s website for an education/careers page. Most are involved in the accreditation process. For example, Googling <national dentist association> finds the American Dental Association's website, which links to the Commission on Dental Accreditation’s listing of schools. Once you know which organization accredits the type of program you wish to apply for, you may try searching that organization's website for a list of schools it has accredited - likely in an education/careers section. Then, cross-check that information with an advisor at your schools of choice.
Remember - if accreditation status is important in your field, make sure to confirm that your potential graduate school program that it has been accredited by the proper organization within an acceptable time frame!
While incomplete, the Database of Accredited Postsecondary Institutions and Programs from the U.S. Department of Education may provide you with some information in this regard. Note also their FAQ section.
There are many online resources that can be used to help you locate a graduate school program in the United States. While there is not one that is 100% comprehensive, making use of a few or several will help make sure you locate the best program to fit your needs.