It's pentagon time!

Find me elsewhere:
Instagram: https://www.instagram.com/philedwardsinc/
Twitter: https://twitter.com/philedwardsinc

Honestly, this free DOD book had everything I needed: https://history.defense.gov/Portals/70/Documents/pentagon/1st50years.pdf?ver=JBe7q7khu4RbRfbcL32geg%3d%3d

That said, here's a nice pop history I used (affiliate link):  
https://amzn.to/3Kfzw97

Here's the breathless (and awesome) coverage in Popular Mechanics:
https://books.google.com/books?id=WNYDAAAAMBAJ&lpg=PA8&pg=RA1-PA8#v=onepage&q&f=false

Here's a ton of construction pics at Library of Congress: https://blogs.loc.gov/picturethis/2021/09/the-pentagon-newly-acquired-construction-photos-by-harold-lang/