Fix — Coleccion El Nuevo Tesoro De La Juventud

The collection is part of a century-long lineage of educational publishing:

A fan-favorite section that answered common curious questions. coleccion el nuevo tesoro de la juventud

Whether you are a collector seeking a nostalgic piece of your childhood, a parent looking for an analog antidote to screen time, or a historian studying mid-20th-century education, this collection remains a genuine treasure. The collection is part of a century-long lineage

Biographies of historical figures that inspired young readers. The Book of Poetry and Narratives: or a historian studying mid-20th-century education

I believe you are referring to the (The New Treasure of Youth Collection), a famous illustrated encyclopedia for young people published originally by W. M. Jackson, Inc. (and later by other publishers like Codex and Grolier).