It could be argued that Elvis Presley's "Don't Be Cruel" was the biggest record of The Elvis Era. It was the #1 song longer than any other song of the era and it was in the top slot on all of the 1956 Billboard charts. Cashbox and Gilbert & Theroux both named it the top song of the year, while Billboard put it at #2.

The Elvis Era was a period of major changes in the music industry.  Of course, there is the obvious shift in the public taste in music with the advent of rock and roll and its appeal to a younger audience.  In addition, the industry became much more competitive.  In 1956, there were 122 songs that were ranked for at least one week in the Billboard top twenty.  By 1963 that number nearly doubled to 194.  Record labels became much more willing to take a gamble with an unknown artist if the record sounded like a hit.  In 1956, 86 different artists put a record in the top twenty.  In 1963, 132 artists achieved a top twenty ranking.  The popular music pie was being cut into many more pieces.  With fewer songs sharing the spotlight in the early years, hits had more longevity.  Of the eighteen songs that reached the top spot in 1956, the average stay in the top spot was 5.7 weeks.  Two records, the double-sided hit "Don't Be Cruel" and "Hound Dog" by Elvis Presley (11 weeks), and "Singing the Blues" by Guy Mitchell (10 weeks), had the longest tenure at #1 for the entire era.  By 1963, the average stay was 2.6 weeks, the longest being "Sugar Shack" by Jimmy Gilmore & The Fireballs (5 weeks).  The success rate for independent labels increased dramatically.  In 1956 only 29 labels had a record in the Billboard top twenty.  By 1963 that number had more than doubled.  In 1956, the six major labels had 56% of the top twenty songs.  By 1963 that number was cut in half to 28%.  The likelihood of a small label getting a song in the top twenty was much greater by 1963.  In 1956, there were 15 labels that had only one top twenty record.  In 1963, there were 32.   

Elvis Presley's "Hound Dog" was the B-side to "Don't Be Cruel" "Don't Be Cruel" achieved a number one ranking on all six of Billboard's charts. "Hound Dog" was in the top spot on the "Juke Box,""Best Seller," "Jockey," "Country," and "R&B" lists -- it was #2 on the "Top 100" list.
Year Top Twenty Songs Top Twenty Artists Top Twenty Labels Number One Songs Number One Song Billboard Number One Song Cashbox Number One Song GT Number One Song EE
1956 112 86 29 12 Heartbreak Hotel Don’t Be Cruel Don’t Be Cruel The Green Door
1957 125 89 39 13 All Shook Up Tammy Love Letters in the Sand Singing the Blues
1958 158 110 53 18 Nel Blu Dipinto Di Blu (Volare) Nel Blu Dipinto Di Blu (Volare) Nel Blu Dipinto Di Blu (Volare) It’s All in the Game
1959 165 107 65 15 The Battle of New Orleans Mack the Knife Mack the Knife Mack the Knife
1960 162 95 60 18 Theme From a Summer Place Theme From a Summer Place Theme From a Summer Place Theme From a Summer Place
1961 184 124 70 20 Tossin’ and Turnin’ Exodus Tossin’ and Turnin’ Tossin’ and Turnin’
1962 195 124 69 20 Stranger on the Shore The Twist Stranger on the Shore The Twist
1963 194 132 68 20 Sugar Shack Limbo Rock The End of the World Sugar Shack