diff --git a/api/auth.js b/api/auth.js
index 3990a8b..0b16e1c 100644
--- a/api/auth.js
+++ b/api/auth.js
@@ -18,7 +18,7 @@ var urls = require('./urls');
  */
 function login(email, password) {
   var config = {
-    url: urls.LOGIN,
+    url: urls.login(),
     body: {
       email: email,
       password: password
diff --git a/api/mosaics.js b/api/mosaics.js
index 0b702f3..5dc217a 100644
--- a/api/mosaics.js
+++ b/api/mosaics.js
@@ -24,7 +24,7 @@ var util = require('./util');
 function get(id, options) {
   options = options || {};
   var config = {
-    url: urls.join(urls.MOSAICS, id),
+    url: urls.mosaics(id),
     terminator: options.terminator
   };
   return request.get(config).then(function(res) {
@@ -51,7 +51,7 @@ function get(id, options) {
 function search(query, options) {
   options = options || {};
   var config = {
-    url: urls.MOSAICS,
+    url: urls.mosaics(),
     query: query,
     terminator: options.terminator
   };
diff --git a/api/quads.js b/api/quads.js
index cd180c4..a253bb4 100644
--- a/api/quads.js
+++ b/api/quads.js
@@ -25,7 +25,7 @@ var util = require('./util');
 function get(mosaicId, quadId, options) {
   options = options || {};
   var config = {
-    url: urls.join(urls.MOSAICS, mosaicId, 'quads', quadId),
+    url: urls.mosaics(mosaicId, 'quads', quadId),
     terminator: options.terminator
   };
   return request.get(config).then(function(res) {
@@ -53,7 +53,7 @@ function get(mosaicId, quadId, options) {
 function search(mosaicId, query, options) {
   options = options || {};
   var config = {
-    url: urls.join(urls.MOSAICS, mosaicId, 'quads', ''),
+    url: urls.mosaics(mosaicId, 'quads', ''),
     query: query,
     terminator: options.terminator
   };
@@ -85,7 +85,7 @@ function search(mosaicId, query, options) {
 function scenes(mosaicId, quadId, options) {
   options = options || {};
   var config = {
-    url: urls.join(urls.MOSAICS, mosaicId, 'quads', quadId, 'scenes', ''),
+    url: urls.mosaics(mosaicId, 'quads', quadId, 'scenes', ''),
     terminator: options.terminator
   };
   return request.get(config).then(function(res) {
diff --git a/api/scenes.js b/api/scenes.js
index 350acee..0a8966a 100644
--- a/api/scenes.js
+++ b/api/scenes.js
@@ -32,7 +32,7 @@ function get(scene, options) {
     };
   }
   var config = {
-    url: urls.join(urls.SCENES, scene.type, scene.id),
+    url: urls.scenes(scene.type, scene.id),
     terminator: options.terminator
   };
   return request.get(config).then(function(res) {
@@ -67,7 +67,7 @@ function search(query, options) {
   }
 
   var config = {
-    url: urls.join(urls.SCENES, type, ''),
+    url: urls.scenes(type, ''),
     query: query,
     terminator: options.terminator
   };
diff --git a/api/urls.js b/api/urls.js
index 37b6c18..f107936 100644
--- a/api/urls.js
+++ b/api/urls.js
@@ -4,27 +4,48 @@
  * @private
  */
 
-var API = require('./config').API_URL;
+var config = require('./config');
 
 /**
  * Join multiple URL parts with slashes.  Note that any trailing and preceeding
  * slashes will be removed from the parts before they are joined.
+ * A single trailing slash can forced by an empty string as the final vararg.
  * @return {string} The joined URL.
  */
 function join() {
-  return Array.prototype.map.call(arguments, function(part) {
+  var components = Array.prototype.map.call(arguments, function(part) {
     if (!(typeof part === 'string' || typeof part === 'number')) {
       throw new Error(
           'join must be called with strings or numbers, got: ' + part);
     }
     return String(part).replace(/^\/?(.*?)\/?$/, '$1');
-  }).join('/');
+  });
+
+  // Preserve trailing slashes but remove every other interstitial.
+  var lastComponent = components.pop();
+  return components
+    .filter(function(el) {
+      return el !== '';
+    })
+    .concat(lastComponent)
+    .join('/');
+}
+
+function rootUrl() {
+  var baseComponents = Array.prototype.slice.call(arguments);
+  return function() {
+    return join.apply(null,
+      [config.API_URL]
+      .concat(baseComponents)
+      .concat(Array.prototype.slice.call(arguments))
+    );
+  };
 }
 
-exports.API = API;
-exports.MOSAICS = join(API, 'mosaics', '');
-exports.SCENES = join(API, 'scenes', '');
-exports.WORKSPACES = join(API, 'workspaces', '');
-exports.LOGIN = join(API, 'auth', 'login');
+exports.api = rootUrl();
+exports.mosaics = rootUrl('mosaics', '');
+exports.scenes = rootUrl('scenes', '');
+exports.workspaces = rootUrl('workspaces', '');
+exports.login = rootUrl('auth', 'login');
 
 exports.join = join;
diff --git a/api/workspaces.js b/api/workspaces.js
index 7da1be7..7bbc640 100644
--- a/api/workspaces.js
+++ b/api/workspaces.js
@@ -8,14 +8,14 @@ var request = require('./request');
 var urls = require('./urls');
 
 function get(id) {
-  var url = urls.join(urls.WORKSPACES, id);
+  var url = urls.workspaces(id);
   return request.get(url).then(function(res) {
     return res.body;
   });
 }
 
 function search() {
-  var url = urls.WORKSPACES;
+  var url = urls.workspaces();
   return request.get(url).then(function(res) {
     return res.body;
   });
diff --git a/test/api/mosaics.test.js b/test/api/mosaics.test.js
index 1a44f07..3e42ca3 100644
--- a/test/api/mosaics.test.js
+++ b/test/api/mosaics.test.js
@@ -9,6 +9,8 @@ var mosaics = require('../../api/mosaics');
 var urls = require('../../api/urls');
 var util = require('../../api/util');
 
+var MOSAICS = 'https://api.planet.com/v0/mosaics/';
+
 describe('api/mosaics', function() {
 
   var mosaic;
@@ -61,7 +63,7 @@ describe('api/mosaics', function() {
       var promise = mosaics.get('one');
       assert.lengthOf(calls, 1);
       var arg = calls[0];
-      assert.equal(arg.url, urls.join(urls.MOSAICS, 'one'));
+      assert.equal(arg.url, urls.join(MOSAICS, 'one'));
 
       promise.then(function(got) {
         assert.deepEqual(got, mosaic);
@@ -130,7 +132,7 @@ describe('api/mosaics', function() {
       var promise = mosaics.search(query);
 
       var arg = calls[0];
-      assert.equal(arg.url, urls.MOSAICS);
+      assert.equal(arg.url, MOSAICS);
       assert.deepEqual(arg.query, query);
 
       promise.then(function(got) {
diff --git a/test/api/quads.test.js b/test/api/quads.test.js
index 870c0b8..84c37ca 100644
--- a/test/api/quads.test.js
+++ b/test/api/quads.test.js
@@ -9,6 +9,8 @@ var quads = require('../../api/quads');
 var urls = require('../../api/urls');
 var util = require('../../api/util');
 
+var MOSAICS = 'https://api.planet.com/v0/mosaics/';
+
 describe('api/mosaics', function() {
 
   var quad;
@@ -66,7 +68,7 @@ describe('api/mosaics', function() {
       assert.lengthOf(calls, 1);
       var arg = calls[0];
       assert.equal(arg.url,
-          urls.join(urls.MOSAICS, 'my-mosaic', 'quads', 'my-quad'));
+          urls.join(MOSAICS, 'my-mosaic', 'quads', 'my-quad'));
 
       promise.then(function(got) {
         assert.deepEqual(got, quad);
@@ -135,7 +137,7 @@ describe('api/mosaics', function() {
       var promise = quads.search('my-mosaic', query);
 
       var arg = calls[0];
-      assert.equal(arg.url, urls.join(urls.MOSAICS, 'my-mosaic', 'quads', ''));
+      assert.equal(arg.url, urls.join(MOSAICS, 'my-mosaic', 'quads', ''));
       assert.deepEqual(arg.query, query);
 
       promise.then(function(got) {
@@ -226,7 +228,7 @@ describe('api/mosaics', function() {
 
       var arg = calls[0];
       assert.equal(arg.url, urls.join(
-          urls.MOSAICS, 'my-mosaic', 'quads', 'my-quad', 'scenes', ''));
+          MOSAICS, 'my-mosaic', 'quads', 'my-quad', 'scenes', ''));
 
       promise.then(function(got) {
         assert.lengthOf(got.features, 1);
diff --git a/test/api/scenes.test.js b/test/api/scenes.test.js
index d529e39..2443539 100644
--- a/test/api/scenes.test.js
+++ b/test/api/scenes.test.js
@@ -9,6 +9,8 @@ var scenes = require('../../api/scenes');
 var urls = require('../../api/urls');
 var util = require('../../api/util');
 
+var SCENES = 'https://api.planet.com/v0/scenes/';
+
 describe('api/scenes', function() {
 
   var get = request.get;
@@ -52,7 +54,7 @@ describe('api/scenes', function() {
       var promise = scenes.get({type: 'foo', id: 'bar'});
       assert.lengthOf(calls, 1);
       var arg = calls[0];
-      assert.equal(arg.url, urls.join(urls.SCENES, 'foo', 'bar'));
+      assert.equal(arg.url, urls.join(SCENES, 'foo', 'bar'));
 
       promise.then(function(got) {
         assert.deepEqual(got, scene);
@@ -71,7 +73,7 @@ describe('api/scenes', function() {
       };
 
       var promise = scenes.get('bar');
-      assert.equal(calls[0].url, urls.join(urls.SCENES, 'ortho', 'bar'));
+      assert.equal(calls[0].url, urls.join(SCENES, 'ortho', 'bar'));
 
       promise.then(function(got) {
         assert.deepEqual(got, scene);
@@ -160,7 +162,7 @@ describe('api/scenes', function() {
       var promise = scenes.search(query);
 
       var arg = calls[0];
-      assert.equal(arg.url, urls.join(urls.SCENES, 'landsat', ''));
+      assert.equal(arg.url, urls.join(SCENES, 'landsat', ''));
       assert.deepEqual(arg.query, query);
 
       promise.then(function(got) {
@@ -191,7 +193,7 @@ describe('api/scenes', function() {
       var promise = scenes.search(query);
 
       var arg = calls[0];
-      assert.equal(arg.url, urls.join(urls.SCENES, 'ortho', ''));
+      assert.equal(arg.url, urls.join(SCENES, 'ortho', ''));
       assert.deepEqual(arg.query, query);
 
       promise.then(function(got) {
diff --git a/test/api/urls.test.js b/test/api/urls.test.js
index fb5899f..1ab7586 100644
--- a/test/api/urls.test.js
+++ b/test/api/urls.test.js
@@ -39,6 +39,9 @@ describe('api/urls', function() {
       }, {
         actual: urls.join('http://example.com', 'foo/', '/bar/', 'bam/'),
         expected: 'http://example.com/foo/bar/bam'
+      }, {
+        actual: urls.join('http://example.com', '', 'foo/', 'bam/', '', ''),
+        expected: 'http://example.com/foo/bam/'
       }];
 
       for (var i = 0, ii = cases.length; i < ii; ++i) {
@@ -72,6 +75,21 @@ describe('api/urls', function() {
       assert.throws(call, Error, 'join must be called with strings or numbers');
     });
 
+    it('works with degenerate cases', function() {
+      var cases = [{
+        actual: urls.join(),
+        expected: ''
+      }, {
+        actual: urls.join('', ''),
+        expected: ''
+      }];
+
+      for (var i = 0, ii = cases.length; i < ii; ++i) {
+        var c = cases[i];
+        assert.deepEqual(c.actual, c.expected, 'case ' + i);
+      }
+    });
+
   });
 
 });