The next time you find yourself cool, calm and collected inside despite it being a scorching 101 degrees outside, direct your thanks toward Williamsburg, where the modern air conditioner was born. In the summer of 1902, the Sackett-Wilhelms Lithographing and Publishing Company at 1013 Grand Street hired 25-year-old engineer Willis Haviland Carrier to tackle fluctuating humidity levels that were altering paper size and causing colored inks to misalign. Carrier devised an ingenious system that passed air through a filter, then over coils containing cold water. The young inventor soon earned a patent for his “apparatus treating air” and, in 1928, rolled out the “Weathermaker”—the first residential AC unit. (Today, the Carrier Corporation remains the world’s largest manufacturer of HVAC systems with sales nearing $12.5 billion.) No longer a publishing warehouse, the Sackett-Wilhelms building is currently home to a mix of industrial tenants, who can take “cold” comfort in knowing their building helped make summer in the city a lot more bearable.