Hamlin and Robert founded the college during the final decades of the Ottoman Empire, and the school grew up inside that friction between worlds. The Ottoman Sultan gave permission for a permanent campus to be built in Bebek, just above the Rumelihisarı fortress, and the first buildings went up on that ridge overlooking the Bosphorus. Getting a Muslim student enrolled in the early years was essentially impossible — the Ottoman government frowned on Muslims attending Christian chapel services, which was then a school requirement — and so the student body was drawn largely from the empire's Christian minorities: Greeks, Armenians, Bulgarians. That mix left its own legacy. Bulgarian politicians and diplomats who had trained at Robert College shaped their country's institutions for decades. A German lecturer named Friedrich Schrader, writing in the 1890s, noted the school's proximity to a Bektashi tekke whose leaders maintained cordial relations with the school's Presbyterian and Congregationalist founders — a snapshot of the unlikely alliances the college drew together.

George Washburn became the college's de facto leader from 1871, officially named president in 1877, and served until 1903. During those years he assembled, in the words of the college catalog, 'a faculty of distinguished scholars who firmly established the college's academic reputation.' Christopher Robert died in 1878, leaving a significant portion of his estate to the institution he had created. The campus expanded. The buildings — neoclassical in style, designed by the American firm Shepley, Rutan and Coolidge — rose one by one against the hillside overlooking the strait. Gould Hall, the oldest educational building still standing, was a gift from Helen Gould Shepard, daughter of the Wall Street financier Jay Gould, who donated $150,000 for its construction in 1911. Its cornerstone was set by the U.S. Ambassador to the Ottoman Empire; inside it is a time capsule. Ionic columns frame the entrance. Ivy and wisteria cover the walls. The campus today covers 65 acres of wooded hillside, and the Bosphorus Beetle — an endemic insect species found nowhere else on Earth — lives here.

By the 20th century, Robert College had grown into something larger than a school. It had a university section, a preparatory academy, and an affiliated women's college — the American College for Girls. The Turkish Republic's modernization demanded homegrown universities, and in 1971 that tension resolved in a remarkable act of institutional generosity: the college donated its Bebek campus — the original ridge-top campus above the Bosphorus — to the Republic of Turkey, which transformed it into Boğaziçi University, one of Turkey's most selective public institutions. Robert College itself relocated to the Arnavutköy campus of the former American College for Girls, where it continues to operate as a private high school. The handover was not a defeat but a deliberate choice, though it left the school straddling an unusual identity — a college in name only, legally a high school, yet maintaining a culture and alumni network of genuinely university-like weight and reach.

Today Robert College accepts between 180 and 220 students per year from a pool of every Turkish student who takes the national LGS examination — only those in the top 0.2 percentile qualify. The roughly 1,000 students on campus at any given time represent Turkey's most academically competitive cohort. In 2011 alone, 53 graduates planned to study abroad, with 8 headed to Ivy League universities; of 79 students who applied abroad, 75 received offers. The school introduced basketball to the Ottoman Empire in 1907. The first student council in Ottoman history was formed here in 1908. It has been the subject of nationalist novels, government pressure, and conspiracy theories — all of which suggest, in their way, how seriously it is taken. The alumni magazine reaches 10,000 graduates worldwide. Orhan Pamuk attended and went on to win the Nobel Prize in Literature. The school's impact on Turkish intellectual and political life over 160 years is quietly enormous, rooted in that unlikely beginning beside the Bosphorus, four students and a borrowed library.