It wasn't Geronimo's Caddilac...

 
Howard Blum, a noted and well-respected author, tells this story:

 As head of the Secret Service, Mike Reilly’s primary job was to keep President Roosevelt safe. FDR didn’t make it easy. In The Night of the Assassins, I write about Mike’s role in foiling an assassination plot against FDR during a secret meeting in Tehran—but his job of protecting the president started much closer to home. 

A little-known piece of American history is that, according to Mike Reilly, FDR borrowed the famous gangster Al Capone’s armored car directly after the Pearl Harbor attack which catapulted the U.S. into World War II. Reilly’s own memoir, Reilly of the White House, tells the story of FDR using the car on December 9, 1941. 

Before borrowing Capone's car, FDR rode in his own custom limousine, the Sunshine Special. This beauty was equipped with 2-way radio, a siren, and extra-wide running boards for Reilly and the other secret service agents to stand on. The problem with The Sunshine Special? The convertible top left the president vulnerable to attack. 

Capone’s armored vehicle was just one of the measures that Mike Reilly and the Secret Service took to protect Roosevelt during his presidency.

 

This is Geronimo's Cadillac...