These databases vary in the amount of information available. You can usually check on the availability of business names, look for addresses and owners. Some databases will also list the registered agent.

    
MASSACHUSETTS
Corporations http://corp.sec.state.ma.us/corpweb/corpsearch/CorpSearch.aspx
Corporation Card File Search (Historical)   http://corp.sec.state.ma.us/CorpWeb/CardSearch/CardSearch.aspx
UCC http://corp.sec.state.ma.us/corp/psearch/default.asp

OTHER STATES click on first letter of state name
A| B| C| D| E| F| G |H| I| J| K| L| M| N| O| P| Q| R| S| T| U| V| W| X| Y| Z

ALABAMA
Corporations http://www.sos.alabama.gov/vb/inquiry/inquiry.aspx?area=Business%20Entity
UCC http://www.sos.state.al.us/BusinessServices/UCC.aspx

ALASKA
Corporations http://commerce.alaska.gov/CBP/Main/CBPLSearch.aspx?mode=Corp
UCC http://dnr.alaska.gov/ssd/recoff/searchUCC.cfm

ARIZONA
Corporations http://starpas.azcc.gov/scripts/cgiip.exe/WService=wsbroker1/main.p
UCC http://www.azsos.gov/apps/ucc/search/

ARKANSAS
Corporations http://www.sosweb.state.ar.us/corps/incorp/
UCC https://www.ark.org/sos/ucc/index.php (fee for online search)

CALIFORNIA
Corporations http://kepler.sos.ca.gov/
UCC http://www.ss.ca.gov/business/ucc (no online search)

COLORADO
Corporations http://www.sos.state.co.us/pubs/business/main.htm
UCC https://www.sos.state.co.us/ucc/pages/home.jspx (requires account set up)

CONNECTICUT
Corporations http://www.concord-sots.ct.gov/CONCORD
UCC http://www.concord-sots.ct.gov/CONCORD

DELAWARE
Corporations https://delecorp.delaware.gov/tin/GINameSearch.jsp
UCC http://www.state.de.us/corp/uccsearch.shtml  (must use “Delaware Authorized Searcher”)

DISTRICT OF COLUMBIA
Corporations https://corp.dcra.dc.gov/Account.aspx/LogOn?ReturnUrl=%2f (must set up account)
UCC http://otr.cfo.dc.gov/page/ucc-uniform-commercial-code-filings  (no online search)

FLORIDA
Corporations http://www.sunbiz.org/search.html
UCC http://www.floridaucc.com/UCCWEB/SearchDisclaimer.aspx

GEORGIA
Corporations http://www.sos.state.ga.us/corporations/corpsearch.htm
UCC http://www.gsccca.org/search/UCC_Search/default.asp

HAWAII
Corporations http://www.ehawaiigov.org/DCCA/biz-name/
UCC https://boc.ehawaii.gov/ucc-maintenance.html  (No online search)

IDAHO
Corporations http://www.accessidaho.org/public/sos/corp/search.html?SearchFormstep=critl
UCC https://www.accessidaho.org/secure/sos/liens/search.html

ILLINOIS
Corporations http://www.cyberdriveillinois.com/departments/business_services/corp.html
UCC http://www.ilsos.gov/uccsearch/

INDIANA
Corporations https://secure.in.gov/sos/online_corps/name_search.aspx
UCC https://secure.in.gov/sos/bus_service/online_ucc/welcome.asp

IOWA
Corporations http://sos.iowa.gov/search/business/(S(ys05ay55boj2f4rgkh0npazy))/search.aspx
UCC http://sos.iowa.gov/search/ucc/search.aspx?ucc

KANSAS
Corporations http://www.accesskansas.org/apps/corporations.html
UCC http://www.kssos.org/business/business_ucc.html (fee service)

KENTUCKY
Corporations https://app.sos.ky.gov/ftsearch/
UCC https://app.sos.ky.gov/ftucc/(S(1wnrb2454z4p0n45y1fltu2z))/search.aspx

LOUISIANA
Corporations http://www.sos.la.gov/BusinessServices/SearchForLouisianaBusinessFilings/Pages/default.aspx (must set up account)
UCC http://www.sos.la.gov/BusinessServices/UniformCommercialCode/HowToSearchForFinancingStatements/Pages/default.aspx (no online search)

MAINE
Corporations http://www.informe.org/icrs/ICRS
UCC https://www.informe.org/ucc/search/begin.shtml (fee service)

MARYLAND
Corporations http://sdatcert3.resiusa.org/ucc-charter/CharterSearch_f.aspx
UCC http://sdatcert3.resiusa.org/ucc-charter/UCCSearch_a.aspx

MASSACHUSETTS
Corporations http://corp.sec.state.ma.us/corpweb/corpsearch/CorpSearch.aspx
Corporation Card File Search (Historical)  http://corp.sec.state.ma.us/CorpWeb/CardSearch/CardSearch.aspx
UCC http://corp.sec.state.ma.us/corp/psearch/default.asp

MICHIGAN
Corporations http://www.cis.state.mi.us/bcs_corp/sr_corp.asp
UCChttps://apps.michigan.gov/UCC/Home.aspx (some searches are not free)

MINNESOTA
Corporations http://mblsportal.sos.state.mn.us/
UCC http://da.sos.state.mn.us/minnesota/home/dahome.asp (most searches are not free)

MISSISSIPPI
Corporations http://www.sos.state.ms.us/busserv/corp/soskb/csearch.asp
UCC http://business.sos.ms.gov/star/portal/msbsd/page/uccSearch-stand/portal.aspx

MISSOURI
Corporations https://www.sos.mo.gov/BusinessEntity/soskb/csearch.asp
UCC https://bsd.sos.mo.gov/ (Requires Account set up)

MONTANA
Corporations https://app.mt.gov/bes/
UCC https://www.montanasos.com/ (Requires Account set up)

NEBRASKA
Corporations https://www.nebraska.gov/sos/corp/corpsearch.cgi?nav=search#searchform
UCC http://www.sos.ne.gov/business/ucc/UCC-EFS_SearchFiling.html (fee service)

NEVADA
Corporations https://nvsos.gov/sosentitysearch/
UCC https://esos.state.nv.us/nvucc/ucc/ (no online search)

NEW HAMPSHIRE
Corporations https://www.sos.nh.gov/corporate/soskb/csearch.asp
UCC https://corp.sos.nh.gov// (fee service)

NEW JERSEY
Corporations https://www.njportal.com/DOR/businessrecords  (Only a business name search, fee for more information)
UCC http://www.nj.gov/treasury/revenue/searchucc.shtml (fee service)

NEW MEXICO
Corporations https://portal.sos.state.nm.us/corps/Corplookup/Lookdn.aspx
UCC https://secure.sos.state.nm.us/ucc/soskb/SearchStandardRA9.asp

NEW YORK
Corporations http://www.dos.state.ny.us/corps/bus_entity_search.html
UCC http://appsext7.dos.ny.gov/pls/ucc_public/web_search.main_frame

NORTH CAROLINA
Corporations http://www.secretary.state.nc.us/corporations/
UCC http://www.secretary.state.nc.us/ucc/FilingSearch.aspx

NORTH DAKOTA
Corporations http://www.nd.gov/sos/businessserv/
UCC http://www.nd.gov/sos/businessserv/centralindex

OHIO
Corporations http://www2.sos.state.oh.us/pls/bsqry/f?p=100:1:1758226593088503::NO:1:P1_TYPE:NAME
UCC http://www2.sos.state.oh.us/pls/bsqry/f?p=100:5:8152591838597889

OKLAHOMA
Corporations https://www.sos.ok.gov/corp/corpInquiryFind.aspx
UCC http://countyclerk.oklahomacounty.org/registrar-of-deeds/ucc

OREGON
Corporations http://egov.sos.state.or.us/br/pkg_web_name_srch_inq.login
UCC https://secure.sos.state.or.us/ucc/searchHome.action

PENNSYLVANIA
Corporations https://www.corporations.state.pa.us/corp/soskb/csearch.asp
UCC https://www.corporations.state.pa.us/ucc/soskb/searchstandardRA9.asp

RHODE ISLAND
Corporations http://ucc.state.ri.us/CorpSearch/CorpSearchInput.asp
UCC http://ucc.state.ri.us/psearch/

SOUTH CAROLINA
Corporations http://www.scsos.com/corp_search.htm
UCC https://ucconline.sc.gov/UCCFiling/UCCMainPage.aspx (fee service)

SOUTH DAKOTA
Corporations http://www.sdsos.gov/busineservices/corporations.shtm
UCC http://sdsos.gov/content/viewcontent.aspx?cat=corporations&pg=/corporations/ucc.shtm

TENNESSEE
Corporations http://www.state.tn.us/sos/bus_svc/corporations.htm
UCC http://www.state.tn.us/sos/bus_svc/ucc.htm

TEXAS
Corporations http://ourcpa.cpa.state.tx.us/coa/Index.html
UCC http://www.sos.state.tx.us/corp/sosda/index.shtml (fee service)

UTAH
Corporations http://www.utah.gov/serv/bes
UCC https://secure.utah.gov/uccsearch/uccs (fee service)

VERMONT
Corporations http://corps.sec.state.vt.us/corpbrow.aspx
UCC http://www.sec.state.vt.us/seek/ucc_seek.htm

VIRGINIA
Corporations https://sccefile.scc.virginia.gov/Find/Business
UCC http://www.scc.virginia.gov/clk/uccsrch.aspx

WASHINGTON
Corporations http://www.secstate.wa.gov/corps/search.aspx
UCC http://www.dol.wa.gov/business/UCC/ucconline.html (no free searches)

WEST VIRGINIA
Corporations http://apps.sos.wv.gov/business/corporations/
UCC http://www.sos.wv.gov/business-licensing/uniformcommercialcode/Pages/default.aspx

WISCONSIN
Corporations http://www.wdfi.org/corporations/crispix/default.asp
UCC http://www.wdfi.org/ucc/search/

WYOMING
Corporations https://wyobiz.wy.gov/Business/FilingSearch.aspx
UCC http://soswy.state.wy.us/Business/UCCHome.aspx (fee service)