What is the significance of the year 1861 in Australia's horse racing history?

The year 1861 is significant in Australia's horse racing history because it marks the inaugural running of the Melbourne Cup, which is one of the most prestigious horse races in the country and a key event in the Australian sporting calendar. The Melbourne Cup has grown to become known as "the race that stops a nation," capturing the imagination of the public and showcasing Australia's rich horse racing culture. Through its long-standing tradition, the Melbourne Cup has become synonymous with Australian identity and is celebrated annually on the first Tuesday of November.

While the other options represent noteworthy events or milestones, they do not relate directly to the history of horse racing in Australia. The Melbourne Cup's establishment is a defining moment in the evolution of horse racing, making it the correct choice for understanding the significance of 1861 in this context.