### Understanding Global Urban Populations: A Focus on New York City and Seoul

The question regarding the most populous city often varies based on the country referenced. In this examination, two cities are highlighted as responses to this question: New York City and Seoul. These cities are the most populous in their respective countries, the United States and South Korea. This comprehensive document explores the demographics, historical development, urban planning, and cultural significance of New York City and Seoul to understand why each can be the answer to the question depending on the country context.

#### New York City, United States

**Geographical Location and Demographics**
New York City, often simply called New York, is located in the northeastern part of the United States. It is comprised of five boroughs: Brooklyn, Queens, Manhattan, The Bronx, and Staten Island, which were consolidated into a single city in 1898. With an estimated population of over 8 million people, it is the most populous city in the United States.

**Historical Overview**
Founded in 1624 as a trading post by Dutch colonists, the settlement was initially called New Amsterdam. In 1664, the city came under English control and was renamed New York after the Duke of York. New York City played a pivotal role in various historical contexts, including as a major port during the American Revolution and later, during the Industrial Revolution, becoming a gateway for immigration.

**Urban Planning and Development**
New York City is known for its significant architectural landmarks and a skyscraper-dominated skyline. The city's urban planning is notable for the 1811 Commissioners' Plan that established the grid pattern that New York is famous for. Modern challenges such as housing affordability, public transportation, and sustainability are ongoing focuses of the city’s urban development strategy.

**Cultural and Economic Influence**
As a cultural hub, New York City boasts a thriving arts scene, including the Broadway theater district, numerous museums, and diverse culinary experiences. Economically, it is a central hub for financial and media industries, housing the New York Stock Exchange and major media outlets.

#### Seoul, South Korea

**Geographical Location and Demographics**
Seoul, the capital and largest metropolis of South Korea, is situated in the northwest part of the country. With a population nearing 10 million in the city proper and over 25 million in the wider metropolitan area, Seoul is the most populous city in South Korea.

**Historical Overview**
The origins of Seoul go back to 18 BC when it was founded as the settlement Wiryeseong. It became a prominent city during the Joseon Dynasty, officially named the capital in 1394. Post the Korean War, Seoul saw rapid reconstruction and further expansion, establishing itself as a symbol of Korea’s economic growth.

**Urban Planning and Development**
Seoul’s urban planning reflects both its historical legacies and its rapid modernization. Efforts to modernize infrastructure while preserving historical sites are evident. The city is renowned for its efficient public transportation system and green spaces amidst high-density housing areas.

**Cultural and Economic Influence**
Culturally, Seoul is a hub of K-pop, Korean cuisine, and cinema, contributing significantly to the global spread of Korean culture, known as the "Korean Wave." Economically, it is pivotal to South Korea with major technology firms like Samsung and LG headquartered here.

#### Conclusion

Both New York City and Seoul serve as excellent examples of urban giants dominating their national landscapes. While New York City captures the essence of a cultural and economic American epicenter, Seoul represents the heart of Korean innovation and culture. Both cities are deeply woven into the fabric of their nations’ identities and are pivotal to understanding the broader socioeconomic and cultural contexts of the United States and South Korea, respectively. Hence, the name of the most populous city indeed varies greatly and is contingent upon the specific national context being referred to.