The C. E. Hooper, Inc. got into the television ratings game in early 1948, initially only surveying viewing in the New York City area. The very first local Hooper report for New York City came out in March of 1948 (I don't know the exact period it covered) and it would be some time before the company expanded into other cities. According to the December 4th, 1949 issue of The Billboard, Chicago was added to Hooper's "tele survey" on February 1st following the opening of the East-Midwest connection via coaxial cable . Additional cities -- Detroit, Philadelphia and Washington among them -- came later.
By the time Hooper released its first national network television ratings survey on June 28th, 1949. The Chicago Tribune reported that the number of cities surveyed ranged from five to 24 but The Billboard wrote that "the initial report is based on random phone calls in 31 tele cities" [2, 3]. The Billboard stated that Hooper would explain discrepancies between local ratings in New York City and the national results by pointing out that most cities don't have the same level of competition as New York (it had seven stations, more than any other city). Hooper would also note that Texaco Star Theater (The Milton Berle Show) was seen in many cities via kinescope and thus many viewers might tune out .
Here are the Top 15 programs from this first national Hooper report, from The Billboard. You can find the exact number of cities for each program and its sponsor at the original article :
|1.||Texaco Star Theater (The Milton Berle Show)||NBC||74.4|
|2.||Arthur Godfrey's Talent Scouts||CBS||73.3|
|4.||Toast of the Town||CBS||54.6|
|5.||Cavalcade of Stars||DuMont||43.1|
|6.||The Fred Waring Show||CBS||42.1|
|7.||The Bigelow Show||NBC||41.6|
|9.||Arthur Godfrey & Friends||CBS||39.9|
|12.||Your Show Time||NBC||34.3|
|13.||Original Amateur Hour||DuMont||33.6|
|14.||Stop the Music||ABC||32.9|
2 Wolters, Larry. "Berle Tops TV Hooper Ratings for Networks." Chicago Daily Tribune. 7 Jul. 1949: B5.
3 "Hooper Issues First Network Tele Ratings." The Billboard. 2 Jul. 1949: 10. (Read online at Google Books).