For Martha Day Zschock, writing and illustrating the Journey Around picture book series (Commonwealth Editions), which has more than 160,000 copies in print, was simply a matter of doing her homework. When she began Journey Around Cape Cod and the Islands from A to Z in 1999, the then third-grade teacher in Hyannis, Mass., was taking a class at the Rhode Island School of Design. "I had to do three pages of an alphabet book," said Zschock, who initially didn't like the assignment. "I brought it in to show my students, and one thing led to another."

In January, Zschock embarks on her fifth trip—after writing about Boston, New York and San Francisco—this time to Washington, D.C. As in the previous books in the series, each letter is used in an alliterative sentence, starting with "America's anthem awakens awe." There is also information about the history of the nation's capital written at a third-grade level and cool facts for older kids, such as the evolution of the flag. As in the previous books, a bird symbolizing the city (in this case, an American eagle) is hidden on each page. And the author's twin Heather, a designer for Peter Pauper Press, designed Washington, D.C., as well as the other books in the series; she is also the coauthor of the book on New York, where she lives.

What makes the success of this series unusual is in part due to its publisher, a regional New England press, which had never planned to do books for children, or books rooted in other parts of the country for that matter. Not that it has changed the press's mission. "We're not a children's book publisher," Commonwealth Editions founder Webster Bull told PW. "We are a publisher of gift-quality nonfiction about the history and beauty of New England, which happens to have as its bestselling series a children's series."

Bull credits the Journey Around series with bringing in 40% of Commonwealth's sales and for helping to make the company profitable this year for the first time since 1998, when it changed its focus from vanity-press book publishing under the name Memoirs Unlimited, to a regular trade house. Although Journey Around Boston from A to Z (2000) was actually the second book in Zschock's series, it was the first one that Commonwealth Editions published. Bull later bought the rights and inventory to the Cape Cod book when its publisher, Covered Bridge Press, went out of business.

Given advance orders for Washington, D.C., Bull is, well, bullish, that it could be the breakout book for the series. Commonwealth is planning an initial print run of 38,000 copies and has hired an outside publicist to arrange a tour for the author in January. Next up: a sixth book. Martha plans to take on "the Windy City," Chicago, next.