You must make a good faith effort to locate your spouse for purposes of service. However, after exhausting reasonable efforts, you can move for a "publication" divorce. This is where the divorce is published in an approved newspaper, thereby giving "notice" to your spouse.
The court will only have jurisdiction over the divorce - it will not be able to divide assets, debts, property, etc.
Talk to an attorney in your area for specific guidance.
You definitely can STILL get divorced. You will have to show "due diligence" in attempting to locate him. An attorney who has expertise in divorce law can help you. Usually service is done by publication. This must all be done technically and procedural correctly in order to end up legally divorced. I STRONGLY suggest you retain counsel.
Publication Divorce is an answer. If, after a diligent search you cannot find him you will be able to divorce him by filing a Petition for Dissolution and serving him by using a newspaper with a general circulation in the county where you reside. This could be the Daily Law Bulletin, The Chicago Tribune, Daily Herald, Sun Times etc..
However only the status of being married is under the jurisdiction of the court. You cannot receive Child Support, Maintenance, Property Distribution or any other relief. You can only get divorced. Everything else is RESERVED.
Hire an Attorney. It will be much easier.
rather than a divorce, maybe you could file a suit in probate court to declare her dead. that way you re the widow or widower and maybe better off financially. talk with a probate lawyer first. if this will not work, then talk to a divorce lawyer about a divorce.
You can file a petition for dissolution of marriage (divorce) against your spouse and rather than serve the petition personally, since you don't know where your spouse is, you will have to publish notice as is required in your particular location. Often that is done by publishing the required notice in a newspaper with general circulation. Your selection of newspaper will probably have a form for you to fill out. This type of service by publication will enable you to get divorced but the court will not be able to distribute property or other assets. If you have children, the issue of support can be reserved by the court. That is, a decision on support will or can be made at a later date. It will probably be relatively inexpensive for you to hire an attorney to do this for you but you can do this by yourself if you choose.