What was the first skyscraper in New York City?
The Singer Building in Manhattan was built and completed in 1908. It was the world's tallest building between the years 1908 and 1909.
Yes, the noun 'skyscraper' is a common noun, a general word for a very tall building. A proper noun is the name of a specific person, place, or thing. A proper noun for the common noun 'skyscraper' is the name of a skyscraper; for example, the Burj Khalifa in Dubai or the Empire State Building in New York City.