When Catharine Bond Hill walked the campus of Williams College as an undergraduate in the mid-1970s, the “whiteness” of the campus was apparent.

“It was certainly clear that there weren’t a lot of students of color there,” said Ms. Hill, who graduated from Williams, a liberal arts college in Williamstown, Mass., in 1976.

“I was well aware that I was with other kids who had a fairly privileged upbringing,” she said. “I do remember running into kids on the Williams campus back then who didn’t have a car parked in the lot; but that was unusual.”

For Ms. Hill, the president of Vassar College in Poughkeepsie, N.Y., that initial awareness planted the seeds of what would become her signature causes: socioeconomic diversity and affordability in higher education. It became her life’s work and the issue she was most focused on as she reflected on her career during an interview in the century-old Yale Club in Midtown Manhattan.

Ms. Hill, 62, recently announced that she would step down from the presidency of Vassar next year.

Since she took over a decade ago, the student body of 2,450 has become the most diverse it has been since the college was founded in 1861.

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Last year, the Jack Kent Cooke Foundation awarded Vassar its inaugural $1 million Cooke Prize for Equity in Educational Excellence for success in attracting and graduating low-income students.

Vassar has more than doubled the number of its low-income students during Ms. Hill’s tenure. The college’s financial aid budget has more than doubled to over $60 million; about 60 percent of current students receive some scholarship aid. Nearly a quarter of Vassar’s current first-year students are eligible for a Pell grant, which is available to students whose annual family income is $40,000 or less.

Elijah Mondesir, 21, a resident of St. Croix in the U.S. Virgin Islands, who graduated from Vassar this spring, was one of them.

Mr. Mondesir, who was raised by his grandmother, grew up in a community where young people graduated from high school and went straight to work.

“My grandmother, however, always stressed education,” he said. “She pushed me, my twin brother and older sister to do well in school. And that’s what kept me going. I never wanted to let her down.”

His hard work caught the eye of a school counselor who helped him apply to colleges, including Vassar. The transition to campus life wasn’t easy, he said, but the college’s weeklong program for first-generation students helped. Each of those students is assigned a counselor to help keep them on track.

“Even so, it took until my junior year to learn how to study and how to manage my time,” Mr. Mondesir said.

Vassar has also increased the number of military veterans in classes through the Posse Foundation’s Veterans Program. Since 2013, Vassar has admitted 41 veterans as freshmen. This year, the first two veterans graduated.

For Tanya Painter, 29, who served in the Army for six years, Vassar’s thousand-acre campus with its manicured lawns and formal gardens was a world away from where she had been stationed at Camp Speicher, near Tikrit, Iraq, deep in the desert. Now a member of Vassar’s class of 2017, Ms. Painter is majoring in sociology. She hopes to eventually study for a master’s degree and join the F.B.I.

Vassar and the G.I. Bill pay her full tuition and education fees, as well as for child care for her 2-year-old daughter. But money is tight, and she works at two part-time jobs.

When Ms. Hill took the helm at Vassar, students like Ms. Painter and Mr. Mondesir hardly existed on campus. “The school had a mission to be diverse, but it wasn’t,” Ms. Hill recalled.

With her prodding, the college made a commitment to being need-blind — not considering an applicant’s financial situation when deciding admission.

The changes at Vassar under Ms. Hill are an example of what she would like to see at other schools. Her mantra: Colleges and universities must recruit smart students, regardless of their circumstances of birth.

Education is the heart of equal opportunity and social and economic mobility, and if the United States is committed to that ideal, “young students have to have the opportunity to go on to higher education in some equitable way,” Ms. Hill said. “It is more important than ever to get a bachelor’s degree, given the increasing income inequality in our society.”

College affordability has been at the forefront of the presidential campaign this year. And for good reason: Since 1980, the total cost of attendance increased 162 percent at four-year public colleges, 168 percent at four-year private nonprofit colleges and 69 percent at community colleges, according to data from the United States Census Bureau, the College Board’s 2015 Trends in Student Aid and the Department of Education’s 2014 Digest of Education Statistics. (Over this same period, median household income grew 12 percent. For families in the bottom 40 percent, average household income increased only 4 percent, while their share of national income fell 17 percent.)

Ms. Hill is well aware that enrolling low-income students is only part of the solution.

“We need to do a better job of providing support services once these students arrive on campus,” she said. Colleges that recruit low-income students need to work harder to help them fit in, feel comfortable on campus and want to stay, she said.

“Early on, we would say to the students, ‘Come, it’s going to be wonderful,’” Ms. Hill said. “But the truth is that for our low-income students, we can’t completely level the playing field. There are kids driving up in BMWs with parents’ credit cards in their pocket. They go to New York City whenever they want to go out to restaurants. It becomes very obvious to these financial aid kids that the difference is huge.”

Another concern for Ms. Hill is the financial pressure colleges face to spend large chunks of their budgets on campus features, which are crucial to attracting students whose parents can pay full tuition.

“Students from the very wealthy families are having a lot invested in them by their families from prenatal care through K through 12,” she said. “When they go out looking for schools, they are looking for certain things for their kids: small classes, great athletic facilities. They are looking for wonderful orchestras and great food, sustainable campuses and single rooms.”

And as schools like Vassar compete for those students, “who are both talented and can pay the full sticker price, it’s a little bit of the arms race,” Ms. Hill said.

As for what she is likely to do next, Ms. Hill is playing her cards very close to the vest. It is clear that she intends to stay focused in some capacity on higher education and affordability.

“After more than a decade of working from within an institution, I am interested in the challenge of continuing to improve access for students from all backgrounds, but from a different perspective,” Ms. Hill said. “It is exciting to think about next steps.”