What caused the shift from the Sub-Saharan Africa being referred to as "Negroland" to now being referred to as "Sub-Saharan Africa"?

There's Sub-Saharan Africa now and then there's the Sahara Desert with the Maghreb in North Africa. Once, this was all formerly "Negroland." Now we have Sub-Saharan Africa, North Africa, and the Horn, also included under the definition "Negroland."