Currently, orders placed in the United States, Boohoo's largest overseas market, are picked and packed in the United Kingdom then sent by plane to the United States, with delivery taking eight to 10 days.
The warehouse in Elizabethtown, Pennsylvania, will open in late northern hemisphere summer, with the PrettyLittleThing brand, Boohoo's most popular in the United States, the first to go live.
Shares in Boohoo were up 9% in late morning trading, paring losses over the last year to 47%.
Boohoo expects sales to fall by 10% to 15% in the first half, before a return to growth in the second half.
He noted that 2020 and 2021 were COVID years with trade skewed to athleisure wear, while trade in 2022 was skewed to occasion wear with post-COVID pent-up demand for events such as weddings.