Washington Mayor Muriel E. Bowser (D). (Nicholas Kamm/AFP/Getty Images)

IT IS open to debate whether the $8.5 billion Maryland has offered to spend to attract Amazon to locate its second headquarters in the state would bring a good return on investment. But, to the credit of Maryland lawmakers, at least the pros and cons of this lucrative incentive package were the subject of an open debate. Unfortunately, the same cannot be said of officials in the District and Virginia, who have cloaked details of their offers to the tech giant in secrecy.

As part of an effort to lure Amazon to a site in Montgomery County, the Maryland legislature gave bipartisan approval to a package proposed by Gov. Larry Hogan (R) of credits, incentives and grants. The incentives are the largest ever offered in Maryland and make up the most lucrative of the bids for HQ2 that have become public. “Once-in-a-lifetime opportunity” is how proponents framed the chance to land 50,000 jobs, while critics saw a “race to the bottom” by jurisdictions seeking to outdo each other with bigger breaks for the giant company. (Amazon chief executive Jeffrey P. Bezos owns The Washington Post.)

Amazon is expected to make a pick by year’s end from the 20 locations identified as finalists, and Mr. Hogan made clear he wanted to give Maryland a jump by having legislative approval in hand. The District and Virginia are among those that have refused to disclose the details of their offers out of a belief that showing their hands would put them at a competitive disadvantage. Mayor Muriel E. Bowser (D) has come under criticism from some members of the D.C. Council for refusing to discuss what she has offered to lure Amazon.

It is disappointing that the District, Virginia and Maryland seem to have adopted such a cutthroat approach when, as we have previously argued, they should be working together as a region. If Amazon were to locate in the Washington area, the benefits — in jobs, spinoff developments and prestige — would extend beyond the one winning locality. So would the challenges — in transportation, housing and education. That’s why the three jurisdictions should collaborate on a joint proposal that would be transparent and thoroughly vetted. That would not only make for a stronger bid but also would help build public buy-in for any subsidy.

Absent such a joint proposal, there should at the very least be an end to the secrecy that surrounds the proposed offers by the District and Virginia.