From Wikipedia:

Ansley Wilcox
(January 27, 1856–January 26, 1930)
was an American scholar, Oxford graduate, prominent lawyer, civil service reform commissioner, New York
political insider and friend of Theodore Roosevelt. After the assassination of William McKinley, on September 14, 1901,
Vice President Roosevelt was sworn in as 26th president of the United States in the library of Wilcox's home
at 641 Delaware Avenue in Buffalo, New York.

The letter is written on a card from the University Club, Madison Square, (In New York City)

The University Club
From Wikipedia

The University Club of New York (also known as University Club or UClub)
is a private social club located at 1 West 54th Street at Fifth Avenue in Manhattan, New York, New York.
It received its charter in 1865, but the origins date back to the autumn of 1861
when a group of college friends, principally Yale alumni, founded the club hoping to extend their collegial ties.
The club is not affiliated with any other University Club or college alumni clubs.