By my informal count the US produced for WWII:
Light carriers, such as the USS San Jacinto (CVL-30) which participated in the Battle of the Philippine Sea, also included a young pilot named George Bush who was later shot down doing ground attacks over Chichijima.
Even smaller escort carriers were capable of combat, for example: providing air support for ground troops at Leyte Gulf.
An escort carrier task group also defeated a Japanese force of battle ships & cruisers off Samar.
Depending on how you count, other reports vary and this source says:
That would make 29 CVs & CVLs built, which would not seem to include the seven (or eight) already in service on December 7, 1941.
Just for general info.
Here is a site on one of those CVE’s—Escort Carriers.
http://www.ussblockisland.org/Beta/Welcome.html
USS Block Island—there were two with that name—CVE-21 and CVE-106. CVE-106 was the replacement for CVE-21, sunk in the Atlantic in May,1944.
The two carriers were manned by the same crew—a first in Navy history. The first carrier served in the Atlantic. The second in the Pacific.
Escort carriers could be built much more quickly than a full size carrier, and many were built to take up the slack until larger carriers could come on line.
My uncle was on both these ships.
When CVE-21 was torpedoed, he spent 13 hours in the water until he was rescued, because the destroyers in the group had to hunt down and sink the U-Boat that sank their ship.
The pictures on this site show what an escort carrier was like.