You can visit United States Patent and Trademark office official website www.uspto.gov. They have all the information pertaining patents including what qualifies to be patented, the functions of USPTO and the procedure. It also includes their branches.
Have you Googled or checked with a search engine. I recommend Ask.com. Phrase a question for Ask. to look for; try U S Patent Office for starters and go from there. The question above you are asking is'PERFECT" for the question. Example "Which site can be researched for patents information in the USA? You'll get a number of hits. Go from there and be surprised. Hope this helps! Ray