This list gives the family's residence for the years of 1935 through 1963 and further traces their movement from Salt Lake City, Utah to Pasadena, California. One side note on this list is how silly and dangerous it is for banks and other financial institutions to use the given or surname of a close relative as a password aid. But back to the issue of directories.
The next screen on Ancestry.com continues the list of directories back to 1928. Here is the entry for that year:
The entry lists the name, the gender, the residence year, the street address, the city location, his occupation, his spouse's name and the title of the directory. Here is the image of the actual directory entry:
Because of my research, I happen to know that the actual paper copies of these directories are on the shelves in The Church History Library in Salt Lake City, Utah and in the Utah State Archives. But why travel to downtown Salt Lake when the same directories are online? That may not always be the case and a visit to a library or archive may be in order.
The additional record sources suggested from the directory entries include business records, school records, church records, insurance records, medical records, land and property records, and so forth. The list of records that could be searched as suggested by these entries is practically endless.
Perhaps you are thinking that this is a rather new source of information and your ancestors lived in the 1800 or earlier? Well, you might want to check the University of Massachusetts at Amherst Libraries list of City and business directories of the United States through 1860. This list is described as follows:
The W.E.B. Du Bois Library houses an extensive collection of early city directories. Genealogical researchers use city directories to obtain information about individuals in specific places at particular points in time. City directories include names, addresses, and occupations. They may also reveal age, marital status, home ownership, and race. In addition, these resources frequently list information regarding churches, cemeteries, schools, local businesses, railways, newspapers, social organizations, town services, and city officials.The list includes directories back into the 1700s. The complete list of directories in this one library is here. The entries on Ancestry.com for City Directories include the years from 1821 to 1989. Think about it. A person born as early as the mid-1700s could appear in a city directory on Ancestry.com.
If you do a search online for "earliest city county directories" you will find hundreds of entries from all over the world. Directories in the United Kingdom, for example, date back into the 1600s. You might want to read about Directories in England and Wales on the FamilySearch Research Wiki. Cyndi's List has 236 links to directory websites. Here is a link to a list of Irish Almanacs and Directories. Directories are certainly not limited to English speaking countries. There are numbers of directories from many of the countries of Europe and beyond.
Obviously, I could go on and on. There are so many avenues for genealogical research, I am appalled when researchers claim to have search everywhere. The real limitation is the time and effort the researcher wants to put forth.