diff --git a/gtsam/nonlinear/PriorFactor.h b/gtsam/nonlinear/PriorFactor.h
new file mode 100644
index 000000000..8d8c67d5c
--- /dev/null
+++ b/gtsam/nonlinear/PriorFactor.h
@@ -0,0 +1,120 @@
+/* ----------------------------------------------------------------------------
+
+ * GTSAM Copyright 2010, Georgia Tech Research Corporation,
+ * Atlanta, Georgia 30332-0415
+ * All Rights Reserved
+ * Authors: Frank Dellaert, et al. (see THANKS for the full author list)
+
+ * See LICENSE for the license information
+
+ * -------------------------------------------------------------------------- */
+
+/**
+ *  @file  PriorFactor.h
+ *  @author Frank Dellaert
+ **/
+#pragma once
+
+#include <gtsam/nonlinear/NonlinearFactor.h>
+#include <gtsam/base/Testable.h>
+
+#include <string>
+
+namespace gtsam {
+
+  /**
+   * A class for a soft prior on any Value type
+   * @addtogroup SLAM
+   */
+  template<class VALUE>
+  class PriorFactor: public NoiseModelFactor1<VALUE> {
+
+  public:
+    typedef VALUE T;
+
+  private:
+
+    typedef NoiseModelFactor1<VALUE> Base;
+
+    VALUE prior_; /** The measurement */
+
+    /** concept check by type */
+    GTSAM_CONCEPT_TESTABLE_TYPE(T)
+
+  public:
+
+    /// shorthand for a smart pointer to a factor
+    typedef typename boost::shared_ptr<PriorFactor<VALUE> > shared_ptr;
+
+    /// Typedef to this class
+    typedef PriorFactor<VALUE> This;
+
+    /** default constructor - only use for serialization */
+    PriorFactor() {}
+
+    virtual ~PriorFactor() {}
+
+    /** Constructor */
+    PriorFactor(Key key, const VALUE& prior, const SharedNoiseModel& model = nullptr) :
+      Base(model, key), prior_(prior) {
+    }
+
+    /** Convenience constructor that takes a full covariance argument */
+    PriorFactor(Key key, const VALUE& prior, const Matrix& covariance) :
+      Base(noiseModel::Gaussian::Covariance(covariance), key), prior_(prior) {
+    }
+
+    /// @return a deep copy of this factor
+    virtual gtsam::NonlinearFactor::shared_ptr clone() const {
+      return boost::static_pointer_cast<gtsam::NonlinearFactor>(
+          gtsam::NonlinearFactor::shared_ptr(new This(*this))); }
+
+    /** implement functions needed for Testable */
+
+    /** print */
+    virtual void print(const std::string& s, const KeyFormatter& keyFormatter =
+                                                 DefaultKeyFormatter) const {
+      std::cout << s << "PriorFactor on " << keyFormatter(this->key()) << "\n";
+      traits<T>::Print(prior_, "  prior mean: ");
+      if (this->noiseModel_)
+        this->noiseModel_->print("  noise model: ");
+      else
+        std::cout << "no noise model" << std::endl;
+    }
+
+    /** equals */
+    virtual bool equals(const NonlinearFactor& expected, double tol=1e-9) const {
+      const This* e = dynamic_cast<const This*> (&expected);
+      return e != nullptr && Base::equals(*e, tol) && traits<T>::Equals(prior_, e->prior_, tol);
+    }
+
+    /** implement functions needed to derive from Factor */
+
+    /** vector of errors */
+    Vector evaluateError(const T& x, boost::optional<Matrix&> H = boost::none) const {
+      if (H) (*H) = Matrix::Identity(traits<T>::GetDimension(x),traits<T>::GetDimension(x));
+      // manifold equivalent of z-x -> Local(x,z)
+      // TODO(ASL) Add Jacobians.
+      return -traits<T>::Local(x, prior_);
+    }
+
+    const VALUE & prior() const { return prior_; }
+
+  private:
+
+    /** Serialization function */
+    friend class boost::serialization::access;
+    template<class ARCHIVE>
+    void serialize(ARCHIVE & ar, const unsigned int /*version*/) {
+      ar & boost::serialization::make_nvp("NoiseModelFactor1",
+          boost::serialization::base_object<Base>(*this));
+      ar & BOOST_SERIALIZATION_NVP(prior_);
+    }
+
+	// Alignment, see https://eigen.tuxfamily.org/dox/group__TopicStructHavingEigenMembers.html
+	enum { NeedsToAlign = (sizeof(T) % 16) == 0 };
+  public:
+	EIGEN_MAKE_ALIGNED_OPERATOR_NEW_IF(NeedsToAlign)
+  };
+
+} /// namespace gtsam
diff --git a/gtsam/slam/PriorFactor.h b/gtsam/slam/PriorFactor.h
index 8d8c67d5c..45bf2e4ed 100644
--- a/gtsam/slam/PriorFactor.h
+++ b/gtsam/slam/PriorFactor.h
@@ -15,106 +15,6 @@
  **/
 #pragma once
 
-#include <gtsam/nonlinear/NonlinearFactor.h>
-#include <gtsam/base/Testable.h>
-
-#include <string>
-
-namespace gtsam {
-
-  /**
-   * A class for a soft prior on any Value type
-   * @addtogroup SLAM
-   */
-  template<class VALUE>
-  class PriorFactor: public NoiseModelFactor1<VALUE> {
-
-  public:
-    typedef VALUE T;
-
-  private:
-
-    typedef NoiseModelFactor1<VALUE> Base;
-
-    VALUE prior_; /** The measurement */
-
-    /** concept check by type */
-    GTSAM_CONCEPT_TESTABLE_TYPE(T)
-
-  public:
-
-    /// shorthand for a smart pointer to a factor
-    typedef typename boost::shared_ptr<PriorFactor<VALUE> > shared_ptr;
-
-    /// Typedef to this class
-    typedef PriorFactor<VALUE> This;
-
-    /** default constructor - only use for serialization */
-    PriorFactor() {}
-
-    virtual ~PriorFactor() {}
-
-    /** Constructor */
-    PriorFactor(Key key, const VALUE& prior, const SharedNoiseModel& model = nullptr) :
-      Base(model, key), prior_(prior) {
-    }
-
-    /** Convenience constructor that takes a full covariance argument */
-    PriorFactor(Key key, const VALUE& prior, const Matrix& covariance) :
-      Base(noiseModel::Gaussian::Covariance(covariance), key), prior_(prior) {
-    }
-
-    /// @return a deep copy of this factor
-    virtual gtsam::NonlinearFactor::shared_ptr clone() const {
-      return boost::static_pointer_cast<gtsam::NonlinearFactor>(
-          gtsam::NonlinearFactor::shared_ptr(new This(*this))); }
-
-    /** implement functions needed for Testable */
-
-    /** print */
-    virtual void print(const std::string& s, const KeyFormatter& keyFormatter =
-                                                 DefaultKeyFormatter) const {
-      std::cout << s << "PriorFactor on " << keyFormatter(this->key()) << "\n";
-      traits<T>::Print(prior_, "  prior mean: ");
-      if (this->noiseModel_)
-        this->noiseModel_->print("  noise model: ");
-      else
-        std::cout << "no noise model" << std::endl;
-    }
-
-    /** equals */
-    virtual bool equals(const NonlinearFactor& expected, double tol=1e-9) const {
-      const This* e = dynamic_cast<const This*> (&expected);
-      return e != nullptr && Base::equals(*e, tol) && traits<T>::Equals(prior_, e->prior_, tol);
-    }
-
-    /** implement functions needed to derive from Factor */
-
-    /** vector of errors */
-    Vector evaluateError(const T& x, boost::optional<Matrix&> H = boost::none) const {
-      if (H) (*H) = Matrix::Identity(traits<T>::GetDimension(x),traits<T>::GetDimension(x));
-      // manifold equivalent of z-x -> Local(x,z)
-      // TODO(ASL) Add Jacobians.
-      return -traits<T>::Local(x, prior_);
-    }
-
-    const VALUE & prior() const { return prior_; }
-
-  private:
-
-    /** Serialization function */
-    friend class boost::serialization::access;
-    template<class ARCHIVE>
-    void serialize(ARCHIVE & ar, const unsigned int /*version*/) {
-      ar & boost::serialization::make_nvp("NoiseModelFactor1",
-          boost::serialization::base_object<Base>(*this));
-      ar & BOOST_SERIALIZATION_NVP(prior_);
-    }
-
-	// Alignment, see https://eigen.tuxfamily.org/dox/group__TopicStructHavingEigenMembers.html
-	enum { NeedsToAlign = (sizeof(T) % 16) == 0 };
-  public:
-	EIGEN_MAKE_ALIGNED_OPERATOR_NEW_IF(NeedsToAlign)
-  };
-
-} /// namespace gtsam
+// Note: PriorFactor has been moved to gtsam/nonlinear. This file has been
+// left here for backwards compatibility.
+#include <gtsam/nonlinear/PriorFactor.h>
\ No newline at end of file