Trace family groups forward to the 1940 US Census. Search for each person in the family group on the US Social Security Index, and try to locate a death record for them. Search for the people who you did not locate a death for here:US Public Records Index.
People in US Public Records database may still be living, or there may be other family member at the same address. Write to them to find out if they knew your ancestor.
Vertical files at the local library
Many local libraries keep a vertical file where you can find newspaper clippings and other resources about people and families who lived in the area. Research the people who have the same surnames or who may have lived and worshiped in the same community as your ancestor.
Historic newspapers tell a great deal about the social life of the people in surrounding communities. They often mention weddings, funerals, church activities, visits from out-of-state, and school or local events. Search the issues that were published during the lifetime of your ancestor to learn about extended family members.
Obituaries often include the names of surviving family members where you can learn the names of members of the family group. Use obituaries to learn the names of people who may still be alive.
Search same surnames on Facebook
Whether you are a fan of Facebook or not, over 1.11 billion people actively use it each month. It may be worth your while to start searching people with similar surnames living in the same locality as your family.
More often than not, extended family members are connecting for the first time and sharing photos and stories on Facebook. You could even start a Facebook Community to find family members. You must not look to find success overnight. If you are consistently sharing content, those searching will hopefully discover you. See Finding Family on Facebook.
Oral and written history
You may have not thought of the following items as oral or written history, but they have definitely been used to find living family members:
Long ago, letter writing used to be the preferred way to communicate with family members from afar. Older living family members may still have old letters they either received or that were given to them after loved ones passed away.
Find out if anyone has old letters in your family. Read through them to learn who wrote the letters and who they were writing, and what they discussed. You may learn the names and whereabouts of other family members.
Personal telephone or address books
Parents and grandparents may still be holding onto those old address books where they used to keep track of all the names and phone numbers of family and friends. Check out each person to see if you know who they are and if they are related to you. Do you know each member of the family group? Who may still be living that can tell you more?
Each member of the family should be given a digital copy of the family photos that exist. Are there any family members who may have the only copy of an old photograph? Do they have photographs of people who have not been identified? Before it is too late, sit down and record the names, dates, and events for each photograph. Find out if there is anyone who may still be alive that you can interview.
Family reunions are a great time to discover other living family. This is easier to determine if everyone knows how they are related. Make the effort to collect information that each attendee knows so that it can be shared with the entire family.
Get to know each family member to find out if they have knowledge about branches of the family you do not know about. You never know what you may learn about your ancestor from relatives who seem remotely related.
Many churches have reunions or homecomings once year. Descendants of original members of the church travel from great distances to attend, and it may be wise to attend this event at least once to connect with others and to see what they remember about your family.
Church anniversary booklets are put together and sold for this event. These booklets often contain the history of the church and its members. Current members take out ads and submit photographs. This gives you a great many leads to follow to learn more about living family members.