The answer is Maharishi Mahesh Yogi and A. C. Bhaktivedanta Prabhupada.
Maharishi Mahesh Yogi gained prominence in the United States during the 1960s and 1970s. He is best known for introducing Transcendental Meditation (TM) to the Western world. His teachings attracted a large following, including celebrities like The Beatles, which helped popularize his practices in America.
Bhagwan Shree Rajneesh, also known as Osho, became active in the United States in the late 1970s and early 1980s. He established a large commune in Oregon, which became a center for his teachings. However, his activities in the U.S. were more prominent in the 1980s.
Swami Vivekananda was active in the United States much earlier, during the late 19th century. He is known for his role in introducing Vedanta and Yoga to the Western world, particularly through his speech at the Parliament of the World's Religions in Chicago in 1893.
A. C. Bhaktivedanta Prabhupada founded the International Society for Krishna Consciousness (ISKCON), also known as the Hare Krishna movement, in the United States in 1966. His efforts in spreading the teachings of the Bhagavad Gita and establishing temples across the country were significant during the 1960s and 1970s.