(Photo by Justin Sullivan/Getty Images)

Amazon has entered the fray of the District’s same-day delivery battle, offering free same-day shipping to its Prime members.

The company announced Thursday that Prime members can place orders on more than 1 million items before noon and have them delivered by 9 p.m. any day of the week in D.C. and 13 other cities. Orders over $35 are free; under that threshold will cost $5.99. Non-Prime members can use the service for $8.99 per order plus $0.99 per item.

But like many services that purport to serve the District, not all of the city is within the coverage area. The four Zip codes east of the Anacostia River as well as 20003, 20593, 20319 and 20002 in Wards 5 and 6 are among those in D.C. proper that aren’t eligible.

Via Amazon.

Yet Amazon is able to offer the service to Zip codes as far away as Manassas and Leesburg.

“Our D.C. coverage area extends north to Olney and Gaithersburg and east to Bowie. We also include Northern Virginia west of the Potomac to Dale City, Manassas, Chantilly, and Leesburg,” Amazon spokeswoman Ana Rigby wrote in an email. Zip code eligibility can be checked at Amazon.com/sameday.

Rigby didn’t respond to questions about what could be hindering the service from operating in those neighborhoods, how Amazon made the decision to exclude them, or if they plan to expand there. “We will continue to expand our delivery capabilities and add more zip codes,” was all she wrote.