439 South Union Street offers 53,223 SF of loft-style office space in a five-story brick, timber and steel mill on Lawrence's established South Union Street office and distribution corridor, one mile from I-495 via South Union Street. The building is an occupied, working address: Placer.ai records 97,600+ on-site visits in the last twelve months, up 36% since 2023, with a Monday–Friday, 8 am–4 pm pattern that reads as workforce, not foot traffic. Exposed timber ceilings, oversized mill windows, free on-site parking and a walkable retail cluster at Plaza 114 give an employer a full-floor, 45,223 SF plate that is hard to find at this price point in the Merrimack Valley.