Welcome to the forum

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The main requirements for getting your wife a visa for the UK are:
- evidence that you are married and in a genuine relationship (your marriage certificate and a family photo should be sufficient as you have been married for 14 years).
- evidence that you have suitable accommodation already sorted out in the UK (i.e. evidence of owning a UK home, or tenancy agreement for a property, or evidence that you can live with family or friends in the UK until you find somewhere of your own)
- evidence that you meet the financial requirement.
The financial requirement is usually the biggest hurdle to meet.
In order to qualify for the visa you have to show that:
a) You (the UK citizen) are already in the UK and you have been working in the same UK job for at least 6 months, earning at least £18,600 annual salary.
OR
a) You (the UK citizen) have a guaranteed job offer in the UK paying at least £18,600 per year and starting within 3 months of returning to the UK AND you have earned at least £18,600 in the US in the last 12 months
OR
c) Between you, you and your wife have at least £62,500 in savings and they have been in your account(s) in full for at least 6 months
There are a couple of other ways to meet the requirement (i.e. non-employment income, pension income or self-employment), but these are the main/most common ones.
See here for more information:
http://www.ukba.homeoffice.gov.uk/visas-immigration/partners-families/citizens-settled/spouse-cp/