Valdivia's expedition recognized what the indigenous inhabitants had long known: a defensible high point in a wide valley is worth claiming. The hill's earliest colonial use was as a place of worship and prayer, particularly during a chicken pox outbreak in 1541 that struck the fledgling settlement. Its strategic value hardened over time. In 1816, Brigadier Manuel Olaguer Feliú of the Royal Engineers designed and built two stone-and-lime forts on the hill, one to the north and one to the south, each able to hold eight or twelve cannons, along with a magazine for ammunition and quarters for the garrison. Fort Hidalgo, completed in 1820, still crowns the hill, and by tradition a cannon is fired from it at exactly noon.

The hill also holds a more sorrowful history. One hillside once served as a cemetery for the dissidents, the burial place for people denied a grave in consecrated ground because they did not follow the official Roman Catholic faith. Protestants, freethinkers, and others judged unworthy by the church of the day were laid here, apart from the faithful. In time their remains were moved to a separate section of the General Cemetery, before that cemetery in turn opened its gates to everyone regardless of creed or station. A monument on the hill now remembers them plainly, dedicated to those who were once disowned by both Heaven and Earth, a quiet act of belated dignity for people their own era refused to honor.

For most of its history the hill was a bare, rough outcrop. Then in 1872 Benjamín Vicuña Mackenna, Santiago's restless intendant, made it his mission to transform the eyesore into a garden. He drove a road across the hill, built a gas-lit chapel at the top, and laid out the fountains, terraces, and lookouts that define it today, including the now-iconic yellow-and-white façade and a sophisticated irrigation system that keeps it green. The labor that carved these winding paths into the stone was largely supplied by convicts, a hard truth beneath the ornamental beauty. Vicuña Mackenna worked with the architect Manuel Aldunate, the builder Enrique Henes, and the stonecutter Andrés Staimbuck to turn raw volcanic rock into one of Santiago's most beloved public parks.

Briefly the hill was also a window on the universe. In 1849 the American naval officer James Melville Gilliss led an astronomical expedition to Chile to measure the solar parallax, setting up an observatory on Santa Lucía. When the expedition ended in 1852, its instruments were sold to the Chilean government and became the nucleus of the country's first National Astronomical Observatory. Today the 65,300-square-meter park draws visitors up past the Neptune Fountain and ornate stairways to a viewpoint that is both a tourist magnet and a favorite place to meet, the terraces shaded and watered by Vicuña Mackenna's irrigation system long after the man himself was gone. At the hill's entrance along the Alameda stands a stone carved with words Valdivia wrote to Emperor Charles V, describing the new land he had conquered, the founder's own voice preserved at the foot of the hill where his city was born.