During the Civil War, he was granted leave from Amherst to serve with the 21st Regiment Massachusetts Volunteer Infantry, eventually achieving the rank of colonel and the command of that unit.

Although initially successful, MAC was criticized by politicians and newspaper editors who felt it was a waste of funding in a state that was growing increasingly industrial.

During his eight months in Sapporo, Clark successfully organized SAC, had a significant impact on the scientific and economic development of the island of Hokkaido, and made a lasting imprint on Japanese culture.

His wife, Clarissa, survived him, however she remained in Hawaii for some time after her husband's death and it was agreed that Williston should adopt both Harriet and Lyman Richards.

[21] In the confusion of the battle, fought in thick woods during a thunderstorm, Clark became separated from his regiment and wandered the Virginia countryside for four days before finding the army again.

"[22] Clark's enthusiasm for the war waned considerably after the Battle of Fredericksburg during which the Union Army suffered severe casualties in repeated charges against a heavily fortified stone wall.

As Clark wrote, In the good time coming, the refining, elevating, and strengthening influences of high intellectual and aesthetic culture will be considered as desirable in the agricultural profession as they are in medicine, law or theology ...

If practical farmers are to remain ignorant of all the higher branches of learning, and to have only the mental discipline and culture of the country public schools, they can never occupy their proper position in society.

"[29] Further, Clark warned that if the decay of rural Massachusetts continued, farming would soon be considered, "degrading in its nature, and designed ... only for those poor, stupid, ignorant, or unfortunate persons.

Elected to the Massachusetts Legislature in 1864, Clark secured a bond for the Town of Amherst enabling it to contribute $50,000 to the construction of the college buildings.

Clark was particularly disappointed with the lack of support from the farming community, writing, "To one who understands fully the greatness of the work which has been done in Amherst … the utter indifference in regard to the college manifested by most of the 75,000 farmers of Massachusetts is truly astounding.

Infuriated by what he called, "time-serving politicians and unprincipled newspapers seeking only to float on the tide of public opinion," Clark resigned in 1879.

[34] Clark was one of the commission of three, appointed by Massachusetts governor John Albion Andrew in 1863, to consider the expediency of establishing a state military academy.

Following the Meiji Restoration in 1867, the new Imperial government of Japan set out upon a path of rapid modernization and recruited many European and American academics and military experts to help expedite the process.

However, in the English version of the contract, "the word 'President' was inserted into the text and initialed by Yoshida Kiyonari (the Japanese Minister to the United States at the time).

"[39] Regardless of title, Clark enjoyed the complete support of the Japanese government in organizing SAC and he exerted principal authority over the college while he was in Japan.

"[41] In establishing SAC, Clark introduced the first American model farm and barn in Japan and the first college military unit in the country.

[42] Clark's direct superior while working at SAC was the Governor of Hokkaido (and future Prime Minister of Japan) Kuroda Kiyotaka.

[43] Hokkaido represented the Japanese frontier at that time and with so much work to be done in colonizing the island, Kuroda welcomed and frequently implemented Clark's advice.

[40] Clark submitted recommendations to the governor on such diverse subjects as converting migratory fisherman into permanent colonists and establishing a textiles industry.

[44] In fact, Clark himself was taken aback by the apparent scope of his influence on colonial affairs, writing to his wife, "Governor Kuroda consults me constantly and always follows my advice.

[46] During classroom lectures, informal evening talks, and outings to collect botanical specimens, Clark discussed morality and urged his students to, "Be gentlemen.

Alumni such as Uchimura Kanzō (founder of the non-church movement, a Japanese Christian society) and Nitobe Inazō (Quaker, educator and diplomat), still known nationwide in Japan, were from the second entering class of the College.

[50][51] During his stay in Hokkaido, Clark examined the local flora and introduced new species of plants and trees from Japan to the United States.

"[52] A painting of Clark's departure, rendered in 1971, hangs in the Prefectural Capitol building in Sapporo and includes a lengthier version of his parting words, "Boys, be ambitious!

"[52] After his retirement from MAC, Clark became interested in a scientific floating college proposed by entrepreneur and real estate developer James O. Woodruff.

[58] The good fortune extended throughout the town of Amherst where, according to biographer John Maki, there was a "craze in mining stocks" as Clark's friends, family, and former academic colleagues became heavily invested in the company.

Student and faculty exchanges were informal for many years until, according to journalist Daniel Fitzgibbons, the early 1960s when "the U.S. State Department contracted with the University to help strengthen the agricultural curriculum at Hokkaido.

[70][71][72] One of the first public works of art in honor of Clark's legacy was a bust placed on the campus of the Hokkaido University in 1926 commemorating the 50th anniversary of the establishment of SAC.

[66] Finally, on the campus of the University of Massachusetts Amherst, the William Smith Clark Memorial, a 0.5-acre (0.20 ha) stone and sculptural garden, was dedicated on October 17, 1991.