Do you only plan to invest $20K for 10-15 years, or do you foresee investing more annually?
If your only concern if for the $20K, a simple answer (probably not the best answer) is to earmark it as your emergency fund and put it into the highest-rate insured CD you can find. Done, and satisfies your requirement to earn more interest than savings account or money market fund. And you can skip the rest below....
However, if you foresee this as the start of larger, longer-term, more proactive investing for you, then more work and planning is required of you. (Doing the hard work up front---planning---makes the later execution much easier.)
It is unwise to take investing advice for Internet strangers without knowing and agreeing with their investing philosophy. Suggest you first read the Boglehead Wiki or book. There is a double bonus to the reading, you will learn the BH beliefs about: (1) how to invest---selecting the best investment asset allocation for you, and (2) where to invest---the different investing accounts available to you.
. Begin at "Getting Started".
Book: Boglehead's Guide to Investing
. Get it from your local library.
Both (Wiki/book) will get you acquainted with the different types of investing accounts and the investment products that are appropriate for those accounts, and for you.
You don't mention whether you are currently investing in an IRA, so assume the answer is "No". A good place to start would be to open a Roth IRA account at Vanguard and purchase a target retirement fund. This will get you the tax-advantaged investment for this year, and you can change the fund later if you wish.
You don't mention whether you have an existing taxable investing account, so assume the answer is "No". A good place to start would be to open a taxable investing account at Vanguard and purchase the most tax efficient funds appropriate for you to own. To begin, you can purchase a money market fund while you finish your readings and make your final funds selection. It is easy to later change from a money market fund, and there will be zero tax consequences to do so.
After above, your money will be at Vanguard (Roth account and taxable account), and we are just waiting for you to come up to speed on your reading, ask your questions, and make your decisions before executing your proactive investing plan.
To keep your appropriate funds and accounts options simple...
Read: Principles of Tax-Efficient Fund Placementhttp://www.bogleheads.org/wiki/Principl ... _Placement
Read: The 3-fund portfoliohttp://www.bogleheads.org/wiki/3-fund_portfolio
Option. Depending upon your federal/state tax brackets, you may want to tweak above suggestion by substituting an intermediate-term muni bond fund for the total bond market fund.
Option. If you wish, you can extend your annual tax-efficient bond space by purchasing US savings bonds.
You don't mention whether you are planning for the education of children.
You don't mention whether your investment planning is to be rolled into an estate plan.
You don't mention how much extra you plan to invest annually. If $6.5K or less, then a Roth IRA may be your best investing option.
The answers to above will help the senior BHs give you much better answers to your questions.
Please consider editing your original post (OP) into this format:
Asking Portfolio Questions: viewtopic.php?f=1&t=6212
d.r.a, not dr.a.