[1] Born in Schiedam, Poortvliet was best known for his drawings[2] of animals and for "Gnomes", a famous series of illustrated books with text by Wil Huygen.

He illustrated various books, among them works by Jaap ter Haar, Leonard Roggeveen [nl] and Godfried Bomans.

[citation needed] For years his works were published by Van Holkema en Warendorf in Bussum, where his "Leven en werken van de Kabouter" (co-authored by Wil Huygen, English title is "Gnomes") went through 59 printings.

[6] His books have been translated into English, French, German, Swedish, Finnish, Spanish, Italian and other languages.

This museum stood in the old, historic Town Hall of Middelharnis, "Fortunately far away from the modern art gang in Amsterdam" as Poortvliet said in an interview.