Retail trade jumped 41 percent last year in Sumas and 22 percent in Blaine, the Washington Department of Revenue reported.
In Blaine, the most significant growth was in e-commerce and mail order sales.
Last year, Blaine tallied $12.3 million in taxable retail sales in that category, a 57.8 percent increase over 2011 and a 515 percent increase compared to 2007.
In 2012, e-commerce represented 4.7 percent of all of Blaine's taxable retail sales; the state average was 1.3 percent.
Seattle-based Amazon.com, which must collect state sales tax for products it ships to Washington addresses, is now the largest contributor to the sales tax in Blaine, City Manager Gary Tomsic told The Bellingham Herald in a story Sunday.
"What we have seen over the last couple of years is e-commerce becoming a significant part of our retail tax revenue," Tomsic said.
A number of mailbox stores have popped up recently in border towns just south of the Vancouver, British Columbia, metro area, the newspaper said.
Blaine Mailboxes Plus owner Christina Hannon said most of her customers are Canadians. They can save money on shipping costs; and some online companies don't ship into Canada, she said. Some customers have told her that they can get packages quicker at a U.S. address and that they save hundreds of dollars a year by having a Blaine mailbox.
Currently in Washington, only online companies that have a physical presence in the state are required to collect sales tax. Congress is considering legislation to increase online sales taxes.