One of the problems is that a person must FIRST seek to identify their ancestors Baptist sub-denomination...remember, there is no such thing as THE Baptist Church...each local congregation is autonomous...and most choose to be part of a larger denominational body...but it is not "required." This is a oversimplification, but it will do for our purposes.
In actuality, there is a multiplicity of Baptist "denominations." In Grace's example, she is talking about Southern Baptist churches...but this same scenario does not hold true for American Baptist life.
By far the larger Baptist sub-denominations in the United States have been the SBC and ABC...IF your ancestor was a part of one of these two organizations (they could have been Primitive, Separate, General, and a list of about 30 other possibilities), then registry is much more possible...check for the state convention annual in that particular state and time period and ordained clergy are normally listed...but usually without a date or place of ordination. If your ancestors was living in 1900 THE BEST PLACE TO START LOOKING is in Lasher's BAPTIST MINISTERIAL DIRECTORY (1899 or 1900, going by memory). This will have an encapsulated timeline for the person (if they returned a survey form!)
Most Baptist colleges/archives/etc. will have a copy of Lasher's directory available (and you can also check with an interlibrary loan service, but it is usually a reference piece that does not circulate.)
IF your ancestor was ABC or SBC, I suggest that you contact either the American Baptist Historical Society, Rochester, New York or the Southern Baptist Historical Library and Archives, Nashville, Tennessee...but first I read the following web page
http://www.crds.edu/abhs/genealogy.htmit gives good information about using Baptist records/archives in your research.