William Penn Brooks was born in South Scituate, Massachusetts in November of 1851. He entered the Massachusetts Agricultural College in 1871 and graduated with high honors in 1875. During his undergraduate years he participated in Dr. William Smith Clark's famous experiments on plant physiology. Brooks remained at the Massachusetts Agricultural College as a graduate student in chemistry and botany. During this time, Brooks accepted an invitation from the Japanese government to go to Sapporo to teach. Brooks arrived in Japan in January, 1877 to continue the work begun by Clark to establish the Sapporo Agricultural School. Immediately after his arrival, he began to deliver lectures on agricultural science and took charge of the directorship of the experimental fields. Brooks worked at the Sapporo Agricultural School for twelve years, four of which he served as the college president. Along with his teaching, Brooks made a great number of contributions as an agricultural advisor for the Sapporo provincial government. He introduced onions, corn, beans, forage and other plants to Japan.
In 1882, Brooks returned to America and married Miss Eva Bancroft Hall. They lived in Sapporo for seven years during which time they had two children. Their daughter, Rachel Bancroft Brooks, married Mr. George Drew in 1907. Their son, Sumner Cushing Brooks, married Matilda Moldenhauer while they were both students at Harvard.
Brooks returned to America with his family in October 1888. On leaving Japan, the government bestowed on him the Fourth Order of Merit and the Cordon of the Rising Sun. In 1920, the Minister of Education in Japan conferred on him the degree of Doctor of Agriculture.
In 1889, Brooks was appointed professor of agriculture at the Massachusetts Agricultural College, and at the same time he began to serve as an engineer at the Massachusetts Agricultural Experiment Station. During this time he introduced soybeans to the United States. In August 1896, Brooks went to Germany with his family and studied at Halle for one year where he received his doctorate. After his return from Germany, Brooks became interested mainly in experimental enterprises. He served as President of the Massachusetts Agricultural College from 1905 until 1906. In 1906, he became director of the Station and he remained connected with the college solely as a lecturer. Brooks was an advisor to the Station until 1921. His contributions to agriculture have been mainly published as reports of the schools, the Experiment Station, the state agricultural department, and the societies to which he was connected. Brooks also authored a textbook in three volumes entitled Agriculture and a collection of his lectures were published under the title Science as Applied to Agriculture. In 1932, the Massachusetts Agricultural College granted Brooks an honorary degree of Doctor of Agriculture.
In 1924 Brooks's wife died; three years later he married Ms. Grace Holden. Brooks cultivated his own garden in Amherst where he lived until his death on March 8, 1938 at the age of 87. In a letter written to one of his students Kingo Miyabe he wrote: "I was born in November, 1851, and to my pleasure I am still living in good health. I can still drive the automobile myself and do all the work in my garden. Nothing gives me more pleasure than cultivating vegetables, fruit-trees, and flowering plants and it is this work that is keeping me in such sound health. Now I have twenty odd kinds of hybrid tea roses and they have been in blossom since the middle of June."