Although various kinds of spoken testimony (for example from court records) are available for many historical periods, “Oral History” as we think of it today tends to refer to interviews that are conducted according to certain guidelines. As such, the range of experiences represented tend to begin no earlier than the later nineteenth century and to extend up to the present.
"The Columbia Center for Oral History (CCOH) was founded by historian and journalist Allan Nevins in 1948 and is credited with launching the establishment of oral history archives internationally."
From: Oral History Archives (Columbia University Libraries)
Searching CLIO for “oral history,” and limiting results to Databases, retrieves more than 14 results. If oral histories are of interest, you might wish to consider these databases.
The most general and extensive resource here is: Oral history online. You may also wish to consider specific programs and initiatives such as: The HistoryMakers, the nation’s largest African American
video oral history collection.