Central is the name of a mysterious and powerful organization within the Federal Government. In addition to coordinating the nation's intelligence community and military responses to homeland security threats, it oversees the Southern Reach itself. It is unclear whether "Central" is an official agency or a code word for senior leadership working in concert together across multiple agencies (e.g. National Security Council).
While officially under Central's jurisdiction, the Southern Reach's mandate allows it to act independently in regards to procuring and processing any and all samples, data, and artifacts from Area X, much to the frustration of Central.
Immediately after the Event that birthed Area X, Central directed vast public resources into the newborn Southern Reach. However, over the decades, Central grew complacent, distracted by global terrorism and increasing environmental disasters, siphoning money and personnel away from Area X. The Southern Reach's abandonment by Central has left it a shadow of its former self, requiring the U.S. Armed Forces to take up most of the agency's former responsibilities overseeing/guarding Area X (including the humiliating duty of basic maintenance of the Southern Reach's own headquarters).
Jackie Severance is a powerful member of Central and the mother of Southern Reach's last director, John Rodrigez (aka Control). Concerned the growing danger from Area X is being ignored by the government, and that the Southern Reach itself may have gone rogue, Jackie forms an alliance with Lowry, another senior leader at Central and the sole survivor from the First Expedition. Forced to work behind the scenes, but motivated by the rising fear of imminent disaster, their faction within Central became increasingly unscrupulous in their attempts to unearth the mysteries of Area X and outrun the encroaching storm.