1st Gen Legendaries

From Pokelibrary

About

In Pokemon Blue, Red & Yellow there are legedary pokemon hidden in secret locations throuhout Kanto. These "Legendary" pokemon are VERY RARE, so rare that there is only 1 on of each per game, and you only get ONE chance to capture them. These Pokemon are some of the strongest in Pokemon history.

Where to Find The Legendaries

Articuno

Articuno can be found in the Seafoam Islands Basement floor. You must have the Soul Badge and the Thunder Badge. You must also possess HM04 Surf and HM06 Strength.

Articuno's Info is as follows: '# 144 Articuno

Pokedex Entry:
Articuno is a legendary pokemon. It is said that when this pokemon flies, snow will fall from the skies.