St. John's Northwestern campus consists of a collection of historic buildings, many with towers and battlements in a style that suggests a Medieval castle, with most of them arranged in a U around the drill field.

• The school's oldest surviving building is the 1857 rectory of St. John Chrysostom Church, a small Picturesque-style house which was repurposed in 1884 as the academy's first dormitory, infirmary and dining hall.^[3]
• Next is the odd Shingle style Memorial Hall, designed by John A. Moller with its two caps and built in 1893 as a recreational building/gymnasium.^[4]
• Next among the surviving buildings is the Dr. Sidney Thomas Smythe house, designed by John A. Moller and built in 1901, an unusual agglomeration of Shingle style (the massing) and Classical Revival (the Doric columns) styles. Smythe, the founder of the school, lived here, calling the house "Rosslyn."^[5]
• Knight Hall classroom building was added in 1902.

• Next was DeKoven Hall, designed in Collegiate Gothic style by Thomas Van Alyea and built in 1906, a four-story barracks/administration building with octagonal towers at the corners and battlements topping the walls.^[6]
• The dining hall and barracks Welles Hall was also added in 1906, designed by Van Alyea in a style similar to DeKoven Hall, but with a large square clock tower.^[7]
• The Beacon is a fieldstone monument built in 1923. It holds an eternal light and displays quotes from St. John's founder.^[8]
• Victory Memorial Chapel was built from 1921 to 1926, modeled by Van Alyea on the chapel at West Point, and clad in lannonstone.^[9]
• In 1927 the school added the two-story Hazelwood Hall designed by Van Alyea, housing barracks and classrooms,^[10] and it was expanded with Scott Johnston Hall in 1930, with a corner turret.^[11]
• Smythe Hall was added in 1929, a classroom designed by Van Alyea in a "castle" style like the previous buildings.^[12]

In 1977 these historic campus buildings were listed on the National Register of Historic Places for the complementary design of many of them and since the school is the oldest military academy in Wisconsin.^[1]

• Ehab Amin, Egyptian basketball player^[13]
• Brandin Podziemski, Professional basketball player for the Golden State Warriors
• Harold Huntley Bassett, United States Air Force major general^[14]
• Ralph Barnes, journalist^[15]
• Ed Bearss, Civil War historian, tour guide, and United States Marine Corps veteran^{[citation needed]}
• Roman R. Blenski, Wisconsin state politician^{[citation needed]}
• Eliot Bostar, member of the Nebraska Legislature
• Martin Breunig, German basketball player^[16]
• Donald Clough Cameron, writer of detective novels and comic books^[17]
• Jack Carson, actor in the 1940s and 1950s^[18]
• Theodore Case, chemist, physicist, inventor of the Movietone sound system^{[citation needed]}
• Ahmad Caver (born 1996), basketball player in the Israeli Basketball Premier League who played for the Memphis Hustle^[19]
• John M. Cavey, Wisconsin state politician^{[citation needed]}
• Tom T. Chamales (SJMA, 1942), writer and veteran of U.S. Army's Merrill's Marauders^{[citation needed]}
• Edward A. Craig (SJMA 1917), U.S. Marine Corps officer who commanded combat units during World War II and the Korean War.^[20]
• Darroll DeLaPorte, American football player in the Milwaukee Badgers^[21]
• Donald Freed, playwright, novelist, teacher and activist^{[citation needed]}
• Daniel Gerber (SJMA 1916), founder and president of Gerber Baby Foods.^[1]
• Nick Gravenites (did not graduate), blues, rock and folk singer for Electric Flag^[22]
• John A. Hazelwood, Wisconsin state politician^[23]
• Reggie Hayes, actor, screenwriter and director^{[citation needed]}
• Trévon Hughes (2006), basketball player in the Israeli National League^[24]
• George Kennan (SJMA 1922), U.S. Ambassador to the USSR (1952) and Yugoslavia. He helped develop the Marshall Plan for reconstruction of Europe after World War II.^[1]
• Monte Merkel, American football player for the Chicago Bears^[25]
• Frank Merrill (SJMA 1967), equestrian^[26]
• Sankar Montoute, American football player for the Tampa Bay Buccaneers.^[27]
• Alex Moyer, American football player for the Miami Dolphins^{[citation needed]}
• Thomas Cebern Musgrave Jr., United States Air Force major general^[28]
• Adam Rapp, novelist, playwright, musician and film director^[29]
• Frank C. Rathje (SJMA, did not graduate, honorary 1959), Chicago banker and lawyer^[30][31]
• Jack Riley, American football player for the Boston Redskins^[32]
• Curtis Roosevelt (NMNA 1948), the eldest grandson of President Franklin D. Roosevelt, was a statesman who served as a delegate representing the United States to the United Nations.^[33]
• Daniel Rostenkowski (SJMA 1946), Illinois Democratic leader in the U.S. House of Representatives.^[34]
• Walter G. Schindler, highly decorated vice admiral in the United States Navy^[35]
• Tony Schumacher, award-winning drag racer^[36]
• Jayapataka Swami (Gordon John Erdman II, SJMA 1965), Hare Krishna guru.
• Martín Torrijos (SJMA 1981), President of Panama.^[37]
• Spencer Tracy (NMNA 1919–1920, non-graduate), two-time Academy Award–winning actor.^[33]
• Ty Warner (SJMA 1962), CEO and founder of Ty Inc., manufacturer of Beanie Babies.^[38]
• Minor Watson, character actor known for films in the 1940s^[39]
• Harold J. Week, Wisconsin state politician^{[citation needed]}
• Ronnie Williams, basketball player^{[citation needed]}
• George Wilson (SJMA 1933), NFL end with the Chicago Bears (1937–46). He later coached the Detroit Lions to the NFL Championship Game, 1957 NFL Championship before becoming the first coach of the Miami Dolphins.
• Harry Wismer, sports broadcaster and the charter owner of the New York Titans (now the New York Jets).^[40]
• Cornelius T. Young, Wisconsin state politician^{[citation needed]}
• Tony Zielinski (SJMA 1979), politician in Milwaukee, Wisconsin^[41]

• Official website