diff --git a/lib/local_calling_guide_repo.rb b/lib/local_calling_guide_repo.rb
new file mode 100644
index 0000000000000000000000000000000000000000..ec91d569e7de4c646fa5f8d20751e0f5ea84f812
--- /dev/null
+++ b/lib/local_calling_guide_repo.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require "nokogiri"
+
+class LocalCallingGuideRepo
+	# @param npa [String] area code (first 3 digits after country code)
+	# @param nxx [String] exchange (digits 4-6)
+	# @return [EMPromise<Hash{Symbol => Float}>] :lat and :lon of the rate center
+	# @raise [RuntimeError] if no prefix data found
+	def find(npa, nxx)
+		EM::HttpRequest.new(
+			"https://localcallingguide.com/xmlprefix.php",
+			tls: { verify_peer: true }
+		).aget(query: { npa: npa, nxx: nxx }).then { |res|
+			doc = Nokogiri::XML.parse(res.response)
+			prefix = doc.at("prefixdata")
+			raise "No prefix data for #{npa}-#{nxx}" unless prefix
+
+			{
+				lat: prefix.at("rc-lat").text.to_f,
+				lon: prefix.at("rc-lon").text.to_f
+			}
+		}
+	end
+end
diff --git a/test/test_local_calling_guide_repo.rb b/test/test_local_calling_guide_repo.rb
new file mode 100644
index 0000000000000000000000000000000000000000..d1e0a2dd7f6b732ac28e1cf7a88b85ef0a323fef
--- /dev/null
+++ b/test/test_local_calling_guide_repo.rb
@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "local_calling_guide_repo"
+
+class LocalCallingGuideRepoTest < Minitest::Test
+	def test_find_returns_lat_lon
+		body = Nokogiri::XML::Builder.new { |xml|
+			xml.root {
+				xml.prefixdata {
+					xml.npa "917"
+					xml.nxx "727"
+					xml.x "0"
+					xml.rc "NEW YORK"
+					xml.region "NY"
+					xml.send(:"rc-lat", "40.739362")
+					xml.send(:"rc-lon", "-73.991043")
+				}
+				xml.prefixdata {
+					xml.npa "917"
+					xml.nxx "727"
+					xml.x "1"
+					xml.rc "NEW YORK"
+					xml.region "NY"
+					xml.send(:"rc-lat", "40.739362")
+					xml.send(:"rc-lon", "-73.991043")
+				}
+			}
+		}.to_xml
+
+		stub_request(
+			:get,
+			"https://localcallingguide.com/xmlprefix.php?npa=917&nxx=727"
+		).to_return(status: 200, body: body)
+
+		result = LocalCallingGuideRepo.new.find("917", "727").sync
+		assert_equal 40.739362, result[:lat]
+		assert_equal(-73.991043, result[:lon])
+	end
+	em :test_find_returns_lat_lon
+
+	def test_find_raises_on_missing_data
+		body = Nokogiri::XML::Builder.new { |xml|
+			xml.root
+		}.to_xml
+
+		stub_request(
+			:get,
+			"https://localcallingguide.com/xmlprefix.php?npa=000&nxx=000"
+		).to_return(status: 200, body: body)
+
+		assert_raises(RuntimeError) do
+			LocalCallingGuideRepo.new.find("000", "000").sync
+		end
+	end
+	em :test_find_raises_on_missing_data
+end