When the first model homes in Northglenn opened to the public, more than 15,000 people showed up for tours in a single day. It was June 30, 1959, and the two- and three-bedroom brick homes ranged in price from $11,700 to $30,000. Within six days, according to historical accounts, buyers had spent $1.375 million — the demand for homes so high that Jordon Perlmutter’s Perl-Mack Enterprises could barely keep up. “Dollar for dollar, America’s greatest home values,” a Perl-Mack advertisement for Northglenn proclaimed. Nearly 60 years later, the Adams County suburb is again gaining notice for the strength of its real estate market. Real estate website Realtor.com last week named the ZIP code covering the original Northglenn neighborhoods — 80233 — one of the 20 hottest housing markets in the U.S.