Significant Dates in Diablo History
From information originally published in El Diablo,
Volume IX No. 4 on February 21, 1936.

Additional information is from "History of Concord  Its Progress and Promise"  by Edna May Andrews and Janet Settle, Arliss Harmon, and Takako Endo.  Published by The Concord Historical Society in 1986.

Additional information is from "Mt. Diablo High School   A History" originally published in 1985 by Mt. Diablo High School with the assistance and contributions of Jack Biedermann, Jan Bergamini, Hart Fairclough, Ruth Galindo, Eloise Honett, Jean Laird, Jan McKinnon, Ted McKinnon, Iola O'Grady, Marge Silva, Jim Tackitt, Shirley Tackitt, Concord Historical Society, and with the generous donation of Frances Steccati Daugherty.
April 1901Mount Diablo Union High School was founded.  Mr. George W. Wright was principal.  The school had two instructors (Mr. Wright and Miss M.L. Groves) and a student body of thirty-five.
Temporary school quarters were established in the two second-floor rooms of the Concord Grammar School (on Willow Pass Road), and a room at the Odd Fellows Hall was equipped for chemistry and physics classes.
There was no athletic program so the boys formed a tennis team.

190248 students were enrolled and a baseball team was formed.

1903The first class, consisting of three members (Helen Godfrey, Elinor Godfrey, and Lucile Busey, who was the first student body president) was graduated.

1904Mt. Diablo Union High School was fully accredited by the University of California, which meant that Diablo grads who completed requirements did not have to take an entrance exam to enter the University.
Leonard L. Martin (who became a well-liked dentist in Concord) and two others were graduated.
Mt. Diablo Union High School's four-room building, which cost $12,000 (to build), was opened... on 3 1/2 acres of land donated by A.W. Maltby.  (This building was finally razed in 1963) 

1905Mt. Diablo's first four year class was graduated, including Ralph Wright, who became a prominent citizen of Martinez.

1907A banner year for Diablo.  An important game was won from Alhambra, a school song was composed and adopted, and electric lights were installed in the school building.

1911The trustees purchased 6 adjoining acres.  Trustees and students laid out a quarter-mile track and built a grandstand.

1912An auditorium was added to the campus.  There were 7 teachers who taught a 10-month school year at a combined salary of $6,750.

1916There were now 163 students and ten teachers.

1917Miss Bertha Romaine accepted the position of principal.  Another teacher was added to the faculty.  A course in biology was added to the curriculum.

1919Diablo had 168 students.

1920A gymnasium was built at Diablo.
This was the largest and the best equipped gymnasium in the county.  It was completed under the direction of Coach Hugh Hunter. 
California's first full physical education program was developed at Mt. Diablo Union High School.

1922This rapidy growing high school had 303 students, twenty full-time instructors, an Americanization director, a librarian, and a nurse.
The Science Building (now known as the Art Building) and shops were built.

1929512 students were attending Mt. Diablo.

February 21, 1936A new building (the English Building) is being completed.  650 students are enrolled, and 31 full time teachers are employed.

1940The Commercial Building was built.

1950The Pete Kramer Gym was built along with the Academic Building and the machine shop.

1963 - 1964A multi-purpose cafeteria (Romaine Hall), an administrative suite and library complex, the Music Building, the Science Building and Home Economics Building were built. 
In addition, the old Science Building (the Art Building) had been remodeled to house a little theater, and graphic arts classrooms.  An addition was made on the shop building and both boys' and girls' gymnasium locker rooms were enlarged.  The Dance Studio was also built. 
Grant Street was closed to through traffic from 7:30 to 4pm.
Image from the 1910 Acta.