Alonzo Eratus Horton (October 24, 1813 – January 7, 1909) was an American real estate developer in the nineteenth century.

Horton was born 1813 in Union, Connecticut, the scion of an old New England family,[1] and grew up in Onondaga County, New York.

By his 20s he had developed a keen entrepreneurial spirit, and in 1834, when he was 21, he began transporting grain by boat from the Lake Ontario port of Oswego, New York, to Canada.

During an Indian attack, he lost a bag of gold dust worth $10,000, but kept the money he had made trading ice.

During the late 1850s and early 1860s, Horton spent some time in the East, even marrying his second wife, a prominent New Jersey woman.

In 1862 Horton returned to California, this time to San Francisco, where he opened a furniture and household goods store at 6th and Market streets.

While there he heard about growing settlement and interest in a small town called San Diego,[4][5] located in far southern California, just north of the Mexico–United States border.

"[6] Upon visiting there, he noticed that while the small town was built around the old Spanish presidio (fortress) well inland near the mouth of the San Diego River, no large settlements had been made along the large San Diego Bay just a few miles south, even though all ships sailing to the town docked in the bay.

Earlier pioneer William Heath Davis was the original founder of San Diego's "New Town", about 12 years before Horton appeared on the scene.

New businesses began to flood into the "Horton's Addition" due to the promise of a rail connection from the harbor to the east.

[1] When the U.S. Congress withdrew its proposed aid to bring the Texas Pacific Railroad into San Diego, the progress of the city froze.

[7] Eventually, the California Southern Railroad (now a part of BNSF Railway) became the first line to connect the city with the rest of America's rail network in 1885.