The donation will go toward purchasing an automated handling system and other technology for the new Nampa library now under construction.
Micron Foundation officials presented Mayor Tom Dale with the check Wednesday morning during a topping off ceremony in which construction crews placed the building's final structural beam.
Staff, construction crews, city leaders and other guests signed the beam before it was hoisted into the sky with a Christmas tree attached.
The 62,000-square-foot library should be complete in early 2015.
In addition to a new city library, the $23 million Library Square project includes a three-story parking garage and office and retail space. A public plaza will have a water feature, landscaping, public art and seating.
Earlier this year demolition crews cleared an entire block between 11th and 12th avenues and 2nd and 3rd streets to make way for the project being developed by Gardner Company.