The maps show how property lines changed over the years, and in many cases there are outlines and pictures of structures.

The creators of the site say this appears to be the first service of its kind in the country, and they hope users will contact them with questions and comments.

"We designed it so a homeowner could find his or her house on the map and find out the lot's history," said professor Mark Leone, who teaches archaeology at College Park. "He or she can tell how big the lot used to be or how small, and how big or small the house used to be."

Dr. Leone said that with "Preservation Search," as the new program is called, "you can find out when the first building was built. You can also find out who used to live in your neighborhood."

The computer program incorporates historical maps and photos, as well as Dr. Leone's own findings gathered over 26 years of archaeological excavations in the city. In 2005, for example, he unearthed West African "hoodoo" artifacts beneath the brick-floor basement of a Charles Street house.

Historian Jean Russo, who works for the Historic Annapolis Foundation and the Maryland State Archives, said the new Web site promises to be a boon for a wide range of people.

"I can tell you that having that type of resources available is invaluable," Ms. Russo said.

The program combines modern technology, such as interactive Geographic Information System maps, with age-old resources such as the Sanborn maps of 1885, which Ms. Russo said should help to make the site an accurate research tool.

"It looks to me like it could be a great deal of fun, and it looks like it could be useful for people ... filing Historic Preservation Commission applications," she said.

Dr. Leone said anyone looking to modify property in the Historic District, for example, will find the site useful when working to comply with regulations.

"The district is tightly regulated and the paperwork requires a detailed knowledge of the historic significance of the property," he said.

Dr. Leone said the program was made possible because of a $70,000 grant from the Maryland Historical Trust and "sweat equity" from the University of Maryland, which paid him and grad students to work in Annapolis during the summers.

Dr. Leone said the city's Office of Planning and Zoning has been especially helpful in providing numerous maps electronically.

Local historian Ginger Doyel, who has published a number of books about Annapolis history, called the new Web site "exciting."

"Any resource that makes our heritage more affordable and accessible is exciting," she said. "It takes time (and money) to go to the State Archives and examine documents, and the Archives has very limited hours."

Ms. Doyel said the State Archives already puts a large number of historical documents online, and recently began offering pictures at MDHISTPICS.net. Now, along comes the new University of Maryland site, which will provide maps.

"It is a wonderful kind of triangle that forms images, documents and maps," she said.

Because the program is new, it might be a bit daunting at first.

The creator of the Web site advised users to be patient when learning how to use the new materials.

"Your casual user would want to go to the main page and read and understand the part about 'Tool Buttons' and the 'About Us' section. Then they can go to the actual server," said Timothy Goddard, who designed the program while a graduate student working with Dr. Leone. He's now working on a Ph.D. at Michigan Technological University.

To avoid frustration, Mr. Goddard said, always remember to turn off the pop-up filter when using this site.

Dr. Leone and Mr. Goddard said they want to hear from users.

"I understand there is going to be a wide variety of questions, and I want the feedback from users," Mr. Goddard said.

Dr. Leone said that if this site proves useful, he hopes to expand it.

"If there is enough interest, we will develop (sites for) Eastport and Parole," Dr. Leone said.

To access Preservation Search, go to http://preservationsearchwebgis.anth.umd.edu/AIAfrontend/index.html.

Users with questions and comments may contact Dr. Leone at mleone@anth.umd.edu, and Mr. Goddard at timdig@gmail.com.