The signs on the homes are basically homeowners in the historic district that are members of or support Riverside Avondale preservation. It doesn't necessarily indicate the home is on the historic register. Riverside/Avondale is a national historic district (1 of only 2 in Jacksonville) and is one of the largest in the country.
If you buy a home in a national historic district there are some restrictions on what can be done to the front exterior of the home (basically what can be viewed from the street) but there are no other guidelines regarding interior renovations or paint colors. This is to protect home values and prevent someone from tearing off their front porch or installing vinyl siding for no good reason. Fairfax and Ortega are not part of the historic district and therefore you have recent teardowns of perfectly good 1920's bungalows.
This area is the most walkable and architecturally & demographically diverse neighborhood in Jacksonville with many parks, restaurants and shops within an easy stroll or bike ride. It is truly a fantastic place to live and work. I live in Riverside and my office is in Avondale and wouldn't have it any other way. If you're interested in the area, feel free to call or email.
David is right, but more specifically you can buy the signs through Riverside/Avondale Preservation (RAP). It it a way of showing that we are proud of our homes and community and support this organization. I would guess that 80-90% of the homes in the district are classified as "contributing structures". There are maps available online at the RAP website which will show you the boundaries of the district. If you do buy a home in the district you are obligated to consult with the city's historic commission before you make any changes to the exterior of your home (with the exception of paint color). This process can be as simple as getting an administrative approval for adding a deck or shed to a full blown hearing if you want to do anything like window replacement or an addition. These restrictions were put into effect to protect the integrity of the neighborhood and ultimately the values of the properties. I am a little biased when it comes to my neighborhood. I have lived here for almost 13 years and remodeled several homes. In my opinion it is the best area in Jacksonville and it just keeps getting better.
You can go to my website for links to the different sites concerning RAP and the city's historic commission's guidelines. You can also call me direct if you would like to be put in contact with some of the key players in the neighborhood and decision making process or if you have interest in the the homes in the area.
Watson Realty Corp.
You can find out lots more details about what the requirements are to have the plaque on the house, other awards for the homes in the area and much more!
Please let us know if you need any further help.
Frank & Sharon Alters