Final answer:
New Zealand first co-hosted the Rugby World Cup in 1987, alongside Australia, marking a significant event in international rugby history.
Step-by-step explanation:
New Zealand first co-hosted the rugby tournament in 1987 with Australia. This inaugural event marked the beginning of what would become one of the premier competitions in international rugby, known as the Rugby World Cup. Notably, this was a significant moment for both New Zealand and Australia as they successfully launched a large-scale sporting event that has continued to grow in popularity and prestige over the years.