Hallen was contracted to capture “… a series of photographs… about once a month… to show construction progress” to satisfy both Washington and the American public.

[1] In addition to showing the construction and progress of the Panama Canal, Hallen depicted the day-to-day life of the “Zonians” – Americans living in the Panama Canal Zone - and its development over the course of the years.

Throughout his 30-year career, Hallen produced between 12,000 and 16,000 images, each with a “strangely satisfying aesthetic experience” portraying life in the Panama Canal Zone.

Hallen retired as the official photographer of the Panama Canal Zone in 1937, after 30 years of service.

Hallen and his wife Maude then moved to Monterey Park, California.