In private life The Masked Raider was cow-town lawyer Lex Wilcox. When justice needs to be done outside of the courtroom, the "cowardly booklovin' lawyer" dons a small mask and strikes out with his horse White Star and his golden eagle Talon. Do not confuse this western hero with The Masked Rider (who is a Marvel Comics property) or with The Masked Rider, a pulp magazine western hero created by Oscar Schisgall for Ranger Publications in 1934, or with The Masked Rider, a television spinoff from (gack!) Mighty Morphin Power Rangers.
Charlton Comics' The Masked Raider ran for thirty issues in its main sequence, from June 1955 to June 1961 -- of course, Charlton's penchant for title and numbering changes may throw this number slightly askew.
Then there was The Masked Raider promotional series under the Charlton imprint Blue Bird Comics. These were comics sent out to various stores (with the store name emblazoned on the cover) to be given away as promotional items. There evidently ten of these items issued from 1959 to 1964. (The comic linked below is a promotional item for Schiff's Shoes.) I assume the stories in the promotional issues were reprints from the main sequence but I'll be happy to corrected.
One confusing thing about this promotional comic is the cover which, although featuring The Masked Raider (and Talon the Golden Eagle!), also has various Charlton characters along the lower part of the cover: Six Gun Heroes, Li'l Genius, Timmy the Timid Ghost, Freddy, and Black Fury -- none of whom are featured in the issue!
This issue has four Masked Raider stories, along with a Texas Rangers tale and a two-page text story.
In the second story, lovely Polly Garrett, who has a crush on The Masked Raider, begins to suspect that the Raider might just be Lex Wilcox. (The resemblance between Wilcox and The Masked Raider is about as obvious as the resemblance between Clark Kent and Superman so the secret identity should be safe, shouldn't it?)