According to historical population numbers:

Historical population
Census Pop. %±
1940 5,909 —
1950 14,405 143.8%
1960 35,943 149.5%
1970 41,021 14.1%
1980 45,165 10.1%
1990 49,847 10.4%
2000 57,746 15.8%
2010 58,829 1.9%

Looks like the 44,500 number quoted in the guide book would put it around the mid to late 1970's - assuming they were trying to be accurate.