Final answer:
Maria Martinez is the best known 20th-century San Ildefonso potter, famous for her black-on-black pottery technique which she developed with her husband Julian.
Step-by-step explanation:
The best known 20th-century San Ildefonso potter was Maria Martinez. Martinez, along with her husband Julian, revolutionized the world of pottery by discovering a technique to produce the now-famous black-on-black pottery, which became highly sought after and helped revive the Pueblo pottery tradition. They taught this technique to others, ensuring the continuation of the craft. While other artists mentioned, such as Pablita Velarde or Manuel Neri, are significant in their own right within their respective disciplines of painting and sculpture, Maria Martinez stands out as the iconic figure in San Ildefonso pottery.