Sir Roger Freeman, KGCHS, was appointed the Western Delegate, and the Most Rev. Leo T. Maher, then Bishop of San Diego, became the Grand Prior for the Delegation. The first west coast investiture for the Western Delegation was held in 1970. Fifty-seven new Knights and Ladies (a large number at that time) were invested in the Immaculata Chapel of the University of San Diego.

The number of Knights and Ladies continued to grow in the western states. The Western Delegation became a full-fledged Lieutenancy in 1973 with 140 Knights and Ladies transferred from the Southern Lieutenancy. The Lieutenancy included Alaska, Arizona, California, Hawaii, Idaho, Montana, Nevada, Oregon, Utah, Washington and Wyoming. Bishop Leo T. Maher was appointed as the Grand Prior of the new Lieutenancy, and H.E. Sir William J. Doyle, was named the first Lieutenant.

Under Sir William Doyle's distinguished leadership, the Western Lieutenancy flourished. From the original 140 charter Knights and Ladies, the Lieutenancy had grown to 490 by the end of 1983. In 1983, Sir William retired as Lieutenant and was succeeded by H.E. Sir John D. Boyce, who had served as treasurer. The Lieutenancy continued to grow at an increasing rate, doubling in size by 1990 to 1,050 members. Bishop Maher died in February 1991. His Eminence Cardinal Roger M. Mahony, Archbishop of Los Angeles succeeded him as Grand Prior.

H.E. Sir John D. Boyce retired after the Investiture and Annual Meeting held in Phoenix in October 1991. The Grand Master, then Cardinal Caprio, appointed Sir George G. Zorn as the new Lieutenant.

By the time of the 1992 Annual Meeting in Anchorage, Alaska, the Lieutenancy had grown to 1,159 Knights and Ladies. The large area of jurisdiction, approximately 3,000 miles north and south and east and west, created an overwhelmingly difficult problem for one Lieutenant and his Council.

A decision was made at the Council Meeting in Anaheim that the Lieutenancy would be divided into the Northwestern and Western Lieutenancy. His Eminence, the Grand Master, Cardinal Caprio accomplished this on November 7, 1993. The Western USA Lieutenancy retained Arizona, Utah, Nevada, Hawaii, and that part of California south of and including Santa Barbara.

The final separation of the Western and Northwestern Lieutenancies occurred in 1994 at the Annual Meeting in Sacramento. At the end of 1996, Knights and Ladies numbered 1009.

At the Annual Meeting in Irvine in October 1998, H.E. Sir James F. McGlone, having served as Treasurer since 1991, was invested as Lieutenant. There were now 1102 Knights and Ladies active in the Lieutenancy.

In 2000, a joint meeting with the with the Northwestern Lieutenancy was held from 29 September to 1 October with more than 800 Knights and Ladies in attendance who were joined by five members of the Grand Magisterium, nine U.S. Lieutenants and Honorary Lieutenants and the Lieutenant of England and Wales. The Governor General of the Order, Ludovicio Carducci Artenisio was accompanied from Rome by Vice Governor General Pier Luigi Parola. The Grand Priors of both Lieutenancies, Cardinal Roger Mahony and Archbishop William Levada presided at the liturgical celebrations with fourteen bishops concelebrating Masses.

Having reached retirement age, H.E. Sir James F. McGlone, was made a Lieutenant of Honor and passed the duties of office to H.E. Sir Patrick D. Powers.

At the 2010 Annual Meeting, the Grand Master, Cardinal John Foley, installed H.E. Sir William H. Davidson as the sixth Lieutenant of the Western USA Lieutenancy. The Governor General, Count Borromeo, Vice Governor General, Jean-Marc Allard, and Chancellor, Rev. Msgr. Hans Brouwers were also in attendance.

Lieutenants of the Western USA Lieutenancy

• H.E. Sir William H. Davidson, KGCHS, Lieutenant, 2010 - Present
• H.E. Sir Patrick D. Powers, KGCHS, Lieutenant, 2002 - 2010
• H.E. Sir James F. McGlone, KGCHS, Lieutenant of Honor, 1998 - 2002
• H.E. Sir George G. Zorn, KGCHS, Lieutenant of Honor, 1991 - 1998
• H.E. Sir John D. Boyce, KGCHS, Lieutenant of Honor, 1983 - 1991
• H.E. Sir William J. Doyle, KGCHS, Lieutenant of Honor, 1973 - 1983

Grand Priors of the Western USA Lieutenancy

• H. Em. Cardinal Roger M. Mahony, Archbishop Emeritus of Los Angeles, 1991 - Present
• H.E. Most Rev. Sir Leo T. Maher, Third Bishop of San Diego, 1973 - 1991