In the early days of Salvador Lutteroth's Empresa Mexicana de Lucha Libre (EMLL) the shows usually featured Americans in the main events with most of the Mexican wrestlers working lower on the cards. With Firpo Segura's boxing background and in-ring skills he became one of the first Mexicans to rise up the ranks of EMLL. often wrestling against various "Foreign menaces" that Lutteroth brought to Mexico. At the EMLL 2nd Anniversary Show Segura lost to American Jack Howland in the semi-main event of the show. Segura's popularity kept growing, making him one of the first Mexican established Main Events, getting top billing all over Mexico. With time Segura was established as the "First Idol of Lucha Libre". Early in his "lucha libre" career Segura began a long running rivalry with Gorila Macías, that led them to face off all over Mexico, including what was supposed to be a boxing match but ended in a wrestling match instead. In 1937 he competed in a tournament to determine the next holder of the Mexican National Middleweight Championship, a tournament that also included his brother Bobby, Black Guzmán, and eventual tournament winner Octavio Gaona among others. ON September 2, 1938 Segura defeated Gaona to win his first wrestling championship, the Middleweight Championship. Due to incomplete records of results for that time period it is not clear exactly when Octavio Gaona regained the championship. For the EMLL 7th Anniversary Show, held on September 12, 1940, Segura teamed up with his longtime rival Macías to defeat the team of Tony Fellitto and "Tigre" Ray Ryan, this match was one of the earliest examples of a "Parejas Increibles" ("Incredible Pairs") match where two rivals were forced to team up for a tag team match. In 1940 Segura defeated Doc Macías, brother of Gorila Macías, in a tournament final to win the Mexican National Heavyweight Championship, underscoring his position as one of the top names of the early days of Lucha Libre. Records are not clear on how many, if any successful title defenses Segura had between 1940 and 1942 when he lost the championship to Ray Duran. Segura regained the championship from Duran in 1943, again with records being unclear on the actual date. By 1943 Segura had become involved in another long running, very intense rivalry, this time with "Enmascarado Rojo" ("The Red Masked Man").